Transcript for Biden pulls ahead in tight swing state races, urges patience
We don't have a final declaration of victory yet. Reporter: Joe Biden addressing a tense nation after another day of uncertainty in America. I know watching these vote tallies on TV moves very slower, slow, and -- as slow as it goes, it can be numbing. But never forget, the tallies aren't just numbers. They represent votes and voters. Men and women who exercised their fundamental right to have their voice heard. Reporter: This evening the former vice president and running mate,or kamala Harris, once again urged calm. We may be opponents but we're we're Americans. Reporter: A clear path to victory remains in sight with Biden on the precipice of a presidency. Look, we both know tensions are high. Let the process work out. As we count all the votes. You know, we're proving again what we've proved for 244 years in this country. Democracy works. Reporter: Poll workers methodically counting around the clock to complete their vote tallies in four battleground states. The race to 270 hinging on Pennsylvania, Arizona, Georgia, and Nevada. Vice president Joe Biden expected to come out on top after pulling ahead in all states. Meanwhile, the president doubled down, even though he has prematurely and falsely declared victory, tonight tweeting, Joe Biden did not wrongfully claim the office of the president. I could make that claim also. Legal proceedings are just now beginning. This all coming after a fiery press conference Thursday night where he baselessly called into question the democratic process. If you count the legal votes, I easily win. If you count the illegal votes, they can try to steal the election from us. What Donald Trump is doing is testing. He's testing the election system. He's testing our institutions more broadly. It is something unamerican. It's alien to who we are. Reporter: The president's supporters reacting to his unfounded claims about a rigged election. We want trump! We want trump! Reporter: Swarming vote counting sites in maricopa county, Arizona, demanding that votes be counted. In Michigan, demanding conversely that they don't. Stop the vote! Stop the vote! Tensions running high on all hundreds of Donald Trump supporters have been showing up at the county recorder's office protesting, some of them armed. State officials are urging patience, promising to count every ballot. Reporter: All eyes ar Pennsylvania. A win here would put Biden over the top. On election day, the former vice president was significantly behind trump in Pennsylvania, but there are more than 1 million mail-in ballots waiting to be counted. Though the president has falsely claimed he won thestate, Biden is now ahead. His lead is expected to grow. Tonight in Philadelphia, celebrations in the street. Biden supporters here are confident that they will win the We're starting to move forward in some democracy. We still have a long way to go. Reporter: Brittany Smalls of black lives matter outside the convention center where votes are being counted. The numbers are reliant on the black community. We're saying we are part of the Reporter: She worked tirelessly to turn out black voters and they came through. Biden overwhelmingly winning the city. 20 we heard the call. And we decided to take action, to turn our anger into action in our communities. Reporter: Philadelphia native pastor Karl day knows about the power of the black vote. It looked early on like black America wasn't going to show up strong at the polls. By tonight, there's a recognition that if, in fact, Joe Biden wins, it's in great part because of black and brown people voting in Philadelphia, in Pittsburgh, in Tucson, and different -- in Atlanta. Detroit. Detroit, yeah. Yes, sir. Yes, sir. Yes, and I wholeheartedly believe that. And I'm truly proud as an African-American man, a pastor, a community leader, that we've shown that what it looks like when we all come together, gather, the power that we do Reporter: At an ABC news town hall with president trump in September, he took the president to task. You've coined the phrase "Make America great again." Right. When has America been great for African-Americans in the ghetto of America? Reporter: Day, undecided at the time, voted for Biden. We wanted to believe the love and celebrate every voter in Philadelphia, whether they voted Republican or Democrat, just to let them know, guess what, we still have to love each other, we have a responsibility. It's ultimately everybody's concern or care with the betterment of all Americans. Reporter: Outside of philly, voters also made big gains for Katie and Morgan Harris live with their two children in westchester, Pennsylvania, a suburb of Philadelphia. In 2016, both voted for trump. I did have this underlying hope that being in the office, being the president, you would act a little more presidential. Reporter: This year they flipped for Biden. I'm just tired of how we speak to each other. Just neighbors, family, friends. On social media. And I think he is leading the way in that. Reporter: They hope their votes can help unify the country. We need to be the united States of America. We need to come together, unite, and move the country forward Reporter: It's been a divisive election cycle. Who's on your list -- Gentlemen, I think -- Reporter: The president facing multiple crises. Hundreds of thousands of Americans dead in the pandemic. The near collapse of the economy. Ongoing racial reckoning. Now perhaps he's facing the consequences. Black lives matter! Black lives matter! Reporter: This has been an electionly defined by early and mail-in voting due to the pandemic, a strategy Democrats strongly encouraged. It was those votes, received before election day, but often counted last, that will likely push Biden over the top. While president trump himself votes by mail, he urged his supporters to vote in person on election day. I like to vote in person. Call me old-fashioned. But a lot of people, a lot of our people want to vote in person. They want to vote. Reporter: Mail-in voting is a legal and secure way to vote. Despite the president calling it fraud. It's a scam. Sending ballots -- Going into the election, looking at the polls, Donald Trump was already looking for some way to delegitimize it and he seized on absentee ballots, what he calls mail-in ballots. Now that these races are so close, in Arizona, he now needs those mail-in ballots in that state, and in other states, to count. He shot himself in the foot. Reporter: President trump set the stage for legal battles he hopes will help him in states where he is lagging behind. We were winning in all the key locations, by a lot, actually, and then our numbers started miraculously getting whittled away, in secret. On I've been told by multiple people close to the president that if this process ends, the legal challenges don't pan out, they fully eect that Donald Trump will give a concession speech. But it will be a very trump-style concession. I'm told that it will be full of complaints about how this election has gone down, suggesting not so much that he lost, but that it was stolen from him. Reporter: Several of the trump lawsuits have already been thrown out due to the lack of evidence. Donald Trump loves to sue people, and he's insistent that he's got to find a a way in court to overturn this election, G to it the supreme court, he said that's what he wants to do. Sounds like Donald Trump wants a lot of recounts in a lot of different states here. The problem with recounts, and it's a tribute to how accurate the counts usually are. In America, recounts don't change that many votes. Reporter: One state guaranteed to see a recount, Georgia, traditionally red state, where Biden now leads by a slim margin. Even Democrats have been surprised by Joe Biden's performance in Georgia. The president's lead at one point was somewhere north of 370,000 votes. Now separated by just mere thousands of votes. The size of a high school. The big question tonight is how many votes are out there to be counted that are already in the bank, in time for the deadline that could possibly affect the outcome of this race? You use your power. The power to vote. Reporter: Part of Biden's edge here, pushed from the Atlanta area and suburbs, where the black vote expanded thanks in part of the efforts of Stacey Abrams. Abrams narrowly missing the race for Georgia's governor. Since then she's spearheaded the fight against voter oppression. Still many stand with claims of voter fraud. Stacey Abrams complains about voter suppression. Their suppression what they're doing to us now as well. Reporter: Other trump supporters say they would respect whoever wins. It's going to take you and me. It's going to take the one on one. It's going to take one on one, every day, each person making a decisive choice to respect the other person regardless of what their political stance is. That's why I'm very clear that I will respect whoever becomes our president. Reporter: At the end of this historic week, a weary and divided nation now watches and waits as democracy plays out in realtime. And next, our political
This transcript has been automatically generated and may not be 100% accurate.