Who's running for president in 2020?

Candidates include Bernie Sanders, Pete Buttigieg, Amy Klobuchar and Joe Biden.

Following Democrats' sweeping victories in the House of Representatives during the 2018 midterm elections, many in the party were eagerly anticipating the 2020 presidential election and the opportunity to unseat President Donald Trump.

The field of candidates remains large, even with candidates dropping out. In November, for example, two people who had earlier ruled out 2020 runs launched presidential campaigns.

Three Republican challengers also declared their intention to run, even as some state party officials were canceling their nominating contests. Former South Carolina Gov. Mark Sanford and former Rep. Joe Walsh, R-Ill., have each since suspended their challenges to Trump in the Republican primary.

Here's a list of all the candidates in the race (in alphabetical order):

Former Vice President Joe Biden

The former vice president and senator from Delaware announced his bid April 25 in an online video.

In the video, he denounced the white supremacists who marched on Charlottesville in 2017 and Trump's response, calling it a "defining moment for this nation in the last few years."

"We are in a battle for the soul of this nation," Biden said in the video.

Biden entered the race with the kind of name recognition that made him a de facto front-runner. But he's also faced questions about accusations from women about unwanted touching, money, messaging, age, identity and ideology in a political environment vastly different from the one he began his career in decades ago.

Former New York City Mayor Michael Bloomberg

Former New York City Mayor Michael Bloomberg officially entered the Democratic primary in November, launching an unconventional pursuit of the party’s presidential nomination after years of flirting with a bid for the nation's highest office.

"I offer myself as a doer and a problem solver -- not a talker. And as someone who is ready to take on the tough fights – and win," Bloomberg said in a statement on his website. "Defeating Trump -- and rebuilding America -- is the most urgent and important fight of our lives. And I’m going all in."

He made a pricey entrance into the race with an eight-figure television ad campaign and advertisements promoting his bio and taking direct aim at President Donald Trump.

His campaign launch, less than three months before the first votes are cast in the Iowa caucuses, added more uncertainty into an already unsettled primary season.

South Bend, Indiana, Mayor Pete Buttigieg

Buttigieg first made a national name for himself with a bid for Democratic National Committee chair in 2017. At 37 years old, he was the youngest candidate in the 2020 race, and could also become the first gay man to be elected president.

While he trailed many of his opponents in name recognition early on, Buttigieg argued that he could represent a generational shift in government, and speaks frequently of issues that will affect younger Americans, such as tax reform, gun control and climate change.

"I get the audacity of somebody like me talking about running for this office, but frankly it's a leap for anybody," Buttigieg said on ABC's "This Week" in February. "And yet all of the people who had that job have been mortals who just bring their experience to the table. My experience is that of guiding a city through transformation, and I think a mayor at any level has the kind of executive frontline government experience and, by the way, problem-solving experience that we need more in Washington right now."

Buttigieg officially entered the race on April 14 at a rally in his hometown of South Bend.

Rep. Tulsi Gabbard, D-Hawaii

Democrat and Iraq War veteran Gabbard announced her presidential bid in January in an appearance on CNN.

"When we stand together, united by our love for each other and for our country, there is no challenge we cannot overcome. Will you join me?" Gabbard tweeted.

Early on in her campaign, the first American Samoan and the first Hindu member of Congress faced questions over her work in the early 2000's for an anti-gay organization run by her father and her defense of Syrian President Bashar al-Assad, with whom she controversially met in 2017.

Sen. Amy Klobuchar, D-Minn.

Klobuchar launched her campaign on a snowy February day in Minneapolis, laying out a platform that included a constitutional amendment to overturn the Citizen's United Supreme Court decision, signing back on to the Paris climate agreement and advocating for criminal justice reform and universal health care.

"I'm running for every parent who wants a better world for their kids," Klobuchar said at her opening rally. "I'm running for every student who wants a good education. For every senior who wants affordable prescription drugs. For every worker, farmer, dreamer, builder. For every American. I'm running for you."

The Minnesota senator is viewed favorably by some in Democratic circles for her ability to perform strongly in her home state -- part of a Midwestern region that helped President Trump to victory in 2016.

Sen. Bernie Sanders, I-Vt.

After a 2016 campaign that saw him amass millions of supporters even as he finished second to Clinton, Sanders entered the 2020 race in February, predicting victory and pointing to the progressive ideas he had championed as an outsider during the last cycle, like "Medicare for All" and free college tuition, that have since become increasingly mainstream.

In an email to supporters announcing the launch of his campaign, Sanders further took aim at Trump, using some of the starkest language of a Democratic candidate up to that point.

"You know as well as I do that we are living in a pivotal and dangerous moment in American history," he wrote. "We are running against a president who is a pathological liar, a fraud, a racist, a sexist, a xenophobe and someone who is undermining American democracy as he leads us in an authoritarian direction."

Tom Steyer

Tom Steyer, a billionaire liberal activist from California, in July became the 26th major Democratic figure to enter the 2020 race, reversing course on a statement he made months earlier saying he wouldn't run.

Steyer has poured millions of his own money into electing Democrats throughout the years, and said in January that he would redouble his efforts to impeach the president instead of seeking the Democratic presidential nomination in 2020. But in a tweet following his presidential campaign announcement, he conceded that his efforts to "hold the president accountable" are "not enough."

In his four-minute announcement video, Steyer unveiled a campaign platform that focused on curbing the influence of corporations in politics and combating climate change.

"Really what we're doing is make democracy work by pushing power down to the people," he said.

President Donald Trump

On the same day he assumed the office of the presidency in 2017, Trump filed preliminary paperwork with the Federal Election Committee (FEC) to qualify as a presidential candidate for 2020.

Trump's re-election campaign announced in early April that it raised more than $30 million in the first quarter of 2019, a total that outpaces all of his Democratic rivals and indicates he will be well-resourced in his bid for a second term in the Oval Office.

"Our prodigious fundraising is further proof of President Trump's clear record of accomplishment on behalf of the American people," wrote Brad Parscale, campaign manager for Trump's re-election campaign.

Sen. Elizabeth Warren, D-Mass.

After establishing a presidential exploratory committee just before New Year's, Warren officially joined the race in February with an event in Massachusetts.

"This is the fight of our lives," the senator said. "The fight to build an America where dreams are possible, an America that works for everyone. I am in that fight all the way."

A prolific fundraiser whose staffers spent time in a number of early primary states assisting other Democrats, Warren said in September that following the midterms she would "take a hard look at running for president," becoming one of the first major names to take steps towards a run.

Former Massachusetts Gov. Bill Weld

Former Massachusetts Gov. Bill Weld announced in April that he's officially running for president, becoming the first Republican to mount a primary challenge against the president.

Weld, a current partner at the Mintz Levin law firm and the 2016 vice presidential candidate for the Libertarian Party, said he would have been "ashamed" if he passed on running against Trump for the Republican party nomination.

"I'd be ashamed of myself if hadn't raised my hand and said, 'Count me in,'" he told ABC News shortly after his announcement. "I think that the president is a very divisive force and that's just not my style, and it's not what Americans deserve."

The following candidates have dropped out of the 2020 election:

Sen. Michael Bennet, D-Colo.

The senior senator from Colorado announced his presidential bid during a May 2 appearance on CBS This Morning, just weeks after a successful prostate cancer operation.

Bennet said his ability to win over Republican constituents and colleagues, and his "broad" experience in the public and private sectors, distinguish him in a crowded Democratic field.

After the polls closed in New Hampshire, he announced he was ending his bid for the White House, but teased that he may be back.

"Tonight is not going to be our night, but let me say this to New Hampshire, you may see me once again," Bennet said.

Sen. Cory Booker, D-N.J.

The New Jersey senator and former mayor of Newark declared his candidacy on Feb. 1 after spending time last year campaigning for Democrats in Iowa, Nevada, South Carolina and Mississippi.

Booker campaigned on a message of unity and collective action, promising to bring Democrats and Republicans together like he has on issues such as criminal justice reform during his time in the Senate.

He suspended his campaign on Jan. 13 - a day before the seventh Democratic debate, which he did not qualify to participate in due to a lack of qualifying polls towards Democratic National Committee polling thresholds, according to ABC News' analysis. It was also a few weeks before the Iowa caucuses where he was expected to finish outside the top tier of candidates -- based on recent polling.

Montana Gov. Steve Bullock

Montana Gov. Steve Bullock is most notably known for winning in 2016 as a Democrat in a state that helped elect Trump.

"As a Democratic governor in a state Trump won by 20 points, I don't have the luxury of only talking to people who agree with me," Bullock said in his May announcement video. "I go all across our state's 147 thousand square miles and look for common ground to get things done."

He campaigned for 202 days, but failed to gain traction at the national level, did not reach 2% in any of the Democratic National Committee qualifying polls and only made one debate stage. He suspended his campaign on Dec. 2 and said in a statement, "While there were many obstacles we could not have anticipated when entering this race, it has become clear that in this moment, I won’t be able to break through to the top tier of this still-crowded field of candidates."

Former Secretary of Housing and Urban Development Julian Castro

Castro, who served as mayor of San Antonio, Texas, before spending over two years in President Barack Obama's cabinet, announced his campaign in his hometown in January.

"I'm running for president because it's time for new leadership, because it's time for new energy, and it's time for a new commitment to make sure that the opportunities I've had are available for every American," he said.

In 2016, Castro was vetted by Hillary Clinton to be her running mate, but the spot ultimately went to Sen. Tim Kaine, D-Va., This year, he said he is eager to restore the style of leadership the nation had under Obama.

Castro dropped out of the race on Jan. 2 after falling short in polling, fundraising, and eventually failing to make the November and December debate stages.

New York City Mayor Bill de Blasio

New York City's mayor released a video on Youtube, announcing his campaign launch on ABC's "Good Morning America."

De Blasio, who is in his second term, joined a crowded field of nearly two dozen Democrats in the race for the White House. The central theme of de Blasio's campaign was "working people first."

On Sept. 20, de Blasio announced he was dropping out of the race. The mayor struggled in the polls and did not qualify for the third round of Democratic primary debates, hosted by ABC News.

"Getting out there, being able to hear people's concerns, address them with new ideas has been an extraordinary experience," he said on MSNBC's "Morning Joe." "But I have to tell you, at the same time I feel like I've contributed all I can to this primary election and it's clearly not my time. So I'm gonna end my presidential campaign, continue my work as mayor of New York City, and I'm gonna keep speaking up for working people."

Former Rep. John Delaney, D-Md.

The Maryland congressman was only seven months into his third term when he announced his candidacy in July 2017, becoming the first member of Congress to launch a bid in the 2020 cycle.

"What the American people are really looking for is a leader to try to bring us together, not actually talk like half the country's entirely wrong about everything they believe," Delaney said on ABC's "This Week" in January 2019, adding, "One of the things I've pledged is in my first hundred days, only to do bipartisan proposals. Wouldn't it be amazing if a president looked at the American people at the inauguration and said, 'I represent every one of you, whether you voted for me or not and this is how I'm going to prove it.'"

On Jan. 31, Delaney announced he was dropping out of the race.

"This race was never about me, but about ideas and doing what’s right for our nation," he said in a statement. "The unique and data-driven ideas that our campaign generated – on how to create a functional universal health care system, price carbon, advance trade, invest in rural America, cure disease, help workers, launch negative emissions technologies, reform education, and expand national service -- are now ideas for the party and I will continue to advocate for them in my next chapter."

Sen. Kirsten Gillibrand, D-N.Y.

The New York Democrat formally announced her presidential run on March 17 in a video posted to her verified YouTube account. In January, she had announced that she was forming a presidential exploratory committee during an appearance on CBS' "The Late Show with Stephen Colbert."

"I'm going to run for president of the United States because, as a young mom, I'm going to fight for other people's kids as hard as I would fight for my own," she said during the interview.

On Aug. 28, Gillibrand announced she was ending her presidential campaign. In a video posted to her Twitter account, Gillibrand thanked her supporters and made a call to action to defeat Trump and secure a Democratic majority in the U.S. Senate.

"We wanted to win this race, but it's important to know when it's not your time, and to know how you can best serve your community and country," she said. "I believe I can best serve by helping to unite us to beat Donald Trump in 2020."

Former Sen. Mike Gravel, D-Alaska

Mike Gravel's unlikely bid for president was launched by two teenagers who learned about him through a podcast and encouraged the former Alaska senator to run for president in 2020.

Having failed to make the debate stage during the first two Democratic debates, Gravel's team decided to close up shop on their campaign and redirect their efforts towards a think tank. In a video posted to Twitter, he endorsed Sanders for president.

His campaign was being transitioned into a progressive think tank called the Gravel Institute.

Sen. Kamala Harris, D-Calif.

Following months of speculation surrounding the junior senator from California, Harris officially announced her 2020 candidacy on ABC's "Good Morning America" in January.

"I love my country. I love my country," she said. "This is a moment in time that I feel a sense of responsibility to stand up and fight for the best of who we are."

If Harris were to win the 2020 presidential election, she would have become the first woman and woman of color to ascend to the nation's highest office. However, she announced the suspension of her presidential bid in December.

"My campaign for president simply doesn’t have the financial resources we need to continue," she said in an email statement to her supporters. "I’m not a billionaire. I can’t fund my own campaign. And as the campaign has gone on, it’s become harder and harder to raise the money we need to compete."

Former Colorado Gov. John Hickenlooper

Hickenlooper joined the field in early March, seeking to parlay his success in growing Colorado's economy while passing environmental regulations and gun control laws into a successful presidential campaign. In a launch video, he spoke further of healing the nation's political divisions.

"One thing I've shown I can do, again and again, is create teams of amazingly talented people and really address these issues that are the critical issues facing this country," he said on "Good Morning America."

He also announced he was suspending his campaign with a video.

"While this campaign didn't have the outcome we were hoping for, every moment has been worthwhile and I'm thankful to everyone who supported this campaign and our entire team," he said in the video posted to Twitter.

Washington Gov. Jay Inslee

Inslee became the first sitting governor to join the presidential field when he kicked off his campaign in early March.

The Washington governor is currently serving his second term in Olympia after more than two decades as a member of Congress, and said that while he is proud of efforts to raise the state's minimum wage and increase access to early childhood education, his presidential bid would prioritize climate change, which he labeled an "existential threat" during his launch event.

On Aug. 21, he announced on MSNBC that he was dropping out of the race.

"It's become clear that I'm not going to be carrying the ball, but we're going to make sure somebody is," he said in the interview.

Miramar, Florida, Mayor Wayne Messam

The little-known Florida mayor joined the growing list of 2020 presidential candidates, announcing his candidacy on March 28 despite facing an uphill climb for his bid.

He announced that he was suspending his presidential campaign on Nov. 20 in a tweet.

"I am Suspending My 2020 Presidential Campaign But I’m Not Finished Yet," he posted on the morning of the fifth Democratic debate in Atlanta.

Messam is currently the chief executive of a city of 140,000 residents -- more than the population of the city Buttigieg runs in Indiana. He is known by many Floridians for playing football for Florida State University in the 1990s.

Rep. Seth Moulton, D-Mass.

Rep. Seth Moulton, a 40-year-old Democrat from Massachusetts, formally announced his presidential bid in April on ABC's "Good Morning America."

Moulton, a Marine veteran who served in Iraq, is known as an outspoken critic of his own party. He was elected to the House in 2013.

During the 2018 midterms, Moulton raised more than $4 million through his Serve America PAC to support Democratic candidates running in battleground states. Before announcing his candidacy, he had already laid groundwork for his 2020 campaign, having visited Iowa, South Carolina, New Hampshire and Nevada.

On Aug. 23, Moulton dropped out of the race. He told The New York Times, "I think it's evident that this is now a three-way race between Biden, Warren and Sanders, and really it's a debate about how far the left wing party should go." He will seek re-election in the House to represent the 6th district of Massachusetts, according to The Times.

Former Rep. Beto O'Rourke, D-Texas

O'Rourke announced an end to his presidential campaign via Twitter on Nov. 1.

"Our campaign has always been about seeing clearly, speaking honestly, and acting decisively. In that spirit: I am announcing that my service to the country will not be as a candidate or as the nominee," he wrote.

He rose national prominence during his unsuccessful run against Texas Sen. Ted Cruz in 2018 and officially announced his presidential campaign in mid-March, calling it "a defining moment of truth for this country and for every single one of us."

Within days, O'Rourke's campaign announced it raised over $6.1 million in the first 24 hours following his announcement, topping Sen. Bernie Sanders' previous high-water mark of $5.9 million.

Former Massachusetts Gov. Deval Patrick

Patrick, the former two-term governor of Massachusetts and the state's first black chief executive, formally announced a bid for the Democratic presidential nomination in a sharp reversal from his 2018 decision to not pursue a run -- injecting more uncertainty into an unsettled primary less than three months before the first votes.

Following his announcement, he traveled to New Hampshire and filed paperwork to appear on the primary ballot. It was a day before the deadline to file.

While in Manchester, New Hampshire, he told ABC News' Whit Johnson, "I wouldn't be in it if I didn't think I could win it."

The day after the New Hampshire primary, he suspended his run and told his supporters in a statement that the outcome in the state wasn't enough to "create the practical wind at the campaign's back to go on to the next round of voting."

Rep. Tim Ryan, D-Ohio

The Ohio Democrat, who announced his candidacy on ABC's "The View" on April 4, billed himself as someone who could unify the progressive wings of the Democratic Party with the more middle-of-the-road working-class voters.

Ryan, a more moderate voice in the crowded field of competitors, rose to the national political stage in 2016 when he launched a failed bid to replace Rep. Nancy Pelosi, D-Calif., as House minority leader. He had previously been floated as a potential candidate in the 2014 Ohio gubernatorial election.

On Oct. 24, he posted a video to announce that he was withdrawing from the presidential campaign.

"While it didn’t work out quite the way we planned, this voice will not be stifled," Ryan said in a statement. "I will continue to advocate and fight for the working people of this country -- white, black, brown, men, women."

Former governor and Rep. Mark Sanford, R-S.C.

Former South Carolina governor and congressman Mark Sanford announced on Sept. 8 that he would challenge the president in the 2020 Republican primary.

"We have a storm coming that we are neither talking about nor preparing for given that we, as a country, are more financially vulnerable than we have ever been since our Nation's start and the Civil War. We are on a collision course with financial reality," he posted on Twitter, outlining his reasons for running.

Two months later, in November, he suspended his bid, telling reporters, "Based on the impossibility of trying to raise the issues I’ve been trying to raise which is debt, deficit, government spending in the midst of an impeachment. So call me a casualty of the impeachment process." He added that he felt it was impossible to get meaningful debate on anything because of partisan fighting over the impeachment inquiry process.

Sanford's tenure as South Carolina governor was rocked by scandal in 2009 after he secretly traveled to Argentina to meet with his lover, Buenos Aires resident Maria Belen Chapur. He confessed to having an extramarital affair in a news conference after his return. He finished his term as governor and was elected to Congress several years later.

Former Rep. Joe Sestak, D-Pa.

Sestak, a former Pennsylvania congressman and a retired three-star admiral in the U.S. Navy, dropped out of the race on Dec. 1. He entered the field at the onset of the first presidential debates in June, despite never qualifying for one.

"I know there is a tear in that fabric right now; but it can be repaired by someone who can lead, and therefore unite, all Americans," Sestak wrote in a Twitter post announcing the end of his candidacy.

Sestak began his career in the Navy in 1974, before becoming the highest-ranking military officer ever elected to Congress in 2007, according to his campaign website. He served in the House until 2011.

In 2016, he competed in the Democratic primary to unseat Sen. Pat Toomey in a tough battleground race but was defeated by Democratic rival Katie McGinty.

Rep. Eric Swalwell, D-Calif.

The California congressman and vocal critic of the president, Swalwell officially launched his bid for the Democratic nomination on April 8. Swalwell, who stopped in several early-voting states during the leadup to his announcement, was rooting his campaign's agenda in the issue of gun control. Following his formal announcement, he held a town hall in Sunrise, Florida, with Marjory Stoneman Douglas High School students and families.

"I'm telling folks, keep your rifles, keep your shotguns, keep your pistols, we just want the most dangerous weapons out of the hands of the most dangerous people," Swalwell told ABC News Chief Anchor George Stephanopoulos on "Good Morning America" on April 9. "Most gun owners believe that."

On July 8, he became the first of the more than 20 Democratic nominees to drop out of the race.

"I ran for President to win and make a difference in our great country," Swalwell wrote in a news release. "I promised my family, constituents, and supporters that I would always be honest about our chances. After the first Democratic presidential debate, our polling and fundraising numbers weren't what we had hoped for, and I no longer see a path forward to the nomination."

Former Rep. Joe Walsh, R-Ill.

Conservative firebrand former Illinois Rep. Joe Walsh announced in August on ABC's "This Week" that he was launching a long-shot Republican presidential primary challenge against the president. Walsh was the second Republican to jump into the primary to challenge Trump.

When ABC News Chief Anchor George Stephanopoulos pointed out the massive uphill climb Walsh had in front of him in the primary, thanks to Trump's overwhelmingly high approval rating within the party, the controversial former congressman argued that conservatives should have an alternative to the president, saying, "I'm running because he's unfit; somebody needs to step up and there needs to be an alternative. The country is sick of this guy's tantrum -- he's a child."

On Feb. 7, three days after the Iowa caucuses, Walsh ended his long-shot bid.

"I’ve suspended my campaign because I’ve concluded that no one can beat Trump in a Republican nomination -- not me, not anyone," Walsh said in a statement. "That was crystal clear to me this week when I stood in front of 3,000 Iowa Republicans and was booed and jeered at for saying we deserve a president who is honest, decent and puts the country first. The Republican party has become a cult."

Marianne Williamson

Author Marianne Williamson announced the launch of her campaign in Los Angeles in January after making six trips to Iowa and one to New Hampshire over the past year as she explored a bid.

Williamson is best known outside of political circles as the author of several popular self-help books and as a "spiritual friend and counselor" to Oprah Winfrey, with multiple appearances on her show and television network. She also ran to represent California's 33rd Congressional District in 2014 as an independent, finishing fourth in the open primary, after endorsements from then-Rep. Keith Ellison, former Govs. Jennifer Granholm and Jesse Ventura, and former Reps. Dennis Kucinich and Alan Grayson.

On Jan. 10, 2020 -- on the eve of early state caucuses -- Williamson suspended her campaign, saying that she didn't want her presence to hurt progressive candidates and recognizing that she would not garner enough votes to move forward.

"These are not times to despair; they are simply times to rise up," she said in a farewell to her supporters. "Things are changing swiftly and dramatically in this country, and I have faith that something is awakening among us. A politics of conscience is still yet possible. And yes ... love will prevail."

Andrew Yang

Yang, an entrepreneur, was running a presidential campaign most commonly noted for its support of universal basic income -- a pledge to provide all Americans 18 and older with $1,000 per month. He spoke frequently about income inequality and the economic transformation that has enriched certain parts of the country while disproportionately harming regions that have failed to keep pace.

Yang was widely regarded as a breakthrough candidate who surpassed the expectation of many as he outlasted sitting senators, former governors and other lifelong politicians as political newcomer. Yang has never held an elected position, yet generated a strong following that carried him through multiple Democratic debates.

Shortly after the polls closed in New Hampshire, Yang announced he was ending his bid.

"While there is great work left to be done -- you know I am the MATH guy -- it is clear tonight from the numbers that we are not going to win this race," he said.