Here's what these potential 2020 candidates focused on:
The Trump and Russia bombshell
Nearly every potential 2020 hopeful wasted no time attacking Trump on Monday's news that the President reportedly revealed classified information to Russian officials last week.
Sen. Kamala Harris, D-Calif., blasted Trump for his "deeply disturbing" action. "[The intelligence community] should not have to worry that anyone, much less the Commander in Chief, might carelessly put their lives in danger by divulging the intelligence they've worked so hard to collect or damage essential relationships with our intelligence sharing partners," she said.
"If there’s some sort of readout of the meeting, a transcript, that means there’s a tape," she Sen. Amy Klobuchar, D-Minn., calling for Congress to obtain a transcript from Trump's meeting with the Russians. "By giving this classified information to them ... that emboldens Russia."
Meanwhile, Sen. Elizabeth Warren, D-Mass., jabbed at Trump, saying the security of the U.S. is more important than Trump's "personal desire to impress his Russian buddies." "I have news for Donald Trump: No matter how much he might admire Vladimir Putin's Russia, here in America, we will never accept autocracy," Warren said.
"This is not business as usual. The president is truly creating chaos," said Sen. Kirsten Gillibrand, adding that Trump's action is "not only irresponsible, but has put lives at risk and undermined our national security." Sen. Cory Booker, D-N.J., said the situation was "more out of a Tom Clancy novel than it should be out of our reality."
Sen. Chris Murphy, D-Conn., expressed concern about the Republicans leading the investigation into Trump and Russia. "No matter who is put into the FBI, they have been sent a pretty clear signal by the White House," he said. "I worry ... that ultimately only a professional special prosecutor can get to the underlying facts here.
Talking to the base: core progressive issues
Sen. Cory Booker gave an emotional address, captivating the audience and speaking at length about the sacrifices by African-Americans that led to his election to the U.S. Senate. "We have so much power as Americans if we keep our hands on the plow," he said. "My calling is not to have this party by what we're against or who we're against," he continued. "Our party cannot just be about that ... Trump is symptom of a problem. He's not the problem."
Sen. Harris focused on drug use in the United States in light of new, stricter sentencing guidelines under the Trump administration. "This administration and Jeff Sessions want to take us back to the dark ages," Harris said. She also called for decriminalizing marijuana and rolling back the influence of private prisons.
Paid family leave was the focus of Sen. Gillibrand's speech, outlining several substantive points about a national 12-week paid family leave proposal. Gov. Bullock focused on the importance of expanding Medicaid in his state, while Los Angeles Mayor Eric Garcetti spoke about raising the minimum wage and local climate change rules.
Sen. Elizabeth Warren mostly stuck to her typical rallying cry around economic inequality, saying that "money is already causing a deep rot in Washington and that is why it's time for systemic change." She also jabbed: "Goldman Sachs now has enough people in the White House to open a branch office."
And Virginia Gov. Terry McAuliffe zeroed in on explaining that the next two election cycles are imperative for redistricting at state and federal levels in 2020. "You need to go back to your states and ask: What are you doing about the map?"
The Washington outsiders
With most of the biggest names in 2020 speculation currently serving in the U.S. Senate, those from outside the beltway pushed their outsider credentials.
Los Angeles Mayor Eric Garcetti postured himself as a Washington outsider who can get things done and focused on why a mayor is uniquely qualified for national leadership. He said people in Los Angeles are "not that different than folks in coal country," adding that the "economy is rapidly changing and leaving so many people behind." "If we define ourselves solely by opposition to this administration, we will sell ourselves short," he said.
Montana Gov. Steve Bullock, who narrowly won re-election in Montana in 2016, where President Trump won by 20 percentage points, also painted himself as a D.C. outsider. "Washington has become a place where talking has often become a substitute for doing," he said, adding that some people think politicians' main goals are to raise money or get more followers on social media.
Tweaking the 2016 strategy
Still other potential 2020 hopefuls were less than subtle about the failed strategy of Democrats in 2016, critiquing Hillary Clinton's campaign for relying too much on data and not listening to everyday Americans, especially in the Midwest.
Sen. Klobuchar said rural areas in America are "not just a place that, oh, we don't win those counties or those regions, so we don't go there." Klobuchar added that not everyone in the U.S. needs a college diploma, highlighting the important education gap in the 2016 race. "We go into areas and we say everyone needs a four-year degree. Well, that's just not true," she said. "We have to allow for different paths for people to follow."
Bullock jabbed the Clinton campaign for its strategy, saying they used data to find supporters and "drag them to the polls" in "those Rust Belt states that we lost in 2016." "There was little attention paid to places that might be difficult to win," he said.
A Republican National Committee spokesperson brought up similar concerns, saying the event "shows how out-of-touch Democrats are with middle class Americans all across the country."