The president was responding to a question about election integrity and said falsely that his campaign's poll watchers were improperly turned away at Philadelphia satellite election offices Tuesday.
"In Philadelphia, they went in to watch, they are called poll watchers. A very safe, very nice thing. They were thrown out. They weren't allowed to watch. You know why? Because bad things happen in Philadelphia. Bad things. I am urging my people, I hope it's going to be a fair election. If it's a fair election," said Trump.
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Action News was there earlier Tuesday as members of the Trump campaign showed up at satellite election offices demanding poll watching certificates, but the poll watchers had not yet been accredited to observe.
Trump's claim was quickly countered by Philadelphia election officials who clarified that no poll watcher certifications for early voting have been issued for anyone. Poll watchers are only certified at polling places on Election Day, not satellite offices.
Trump also suggested widespread Democratic fraud because a handful of ballots were improperly thrown in the trash last week -- but didn't mention it occurred in a Republican-controlled elections office and was quickly reported to authorities.
Tuesday's debate was marked by angry interruptions and bitter accusations between Trump and Democratic challenger Joe Biden.
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Trump and Biden arrived in Cleveland hoping the debate would energize their bases of support, even as they competed for the slim slice of undecided voters who could decide the election. It has been generations since two men asked to lead a nation facing such tumult, with Americans both fearful and impatient about the coronavirus pandemic that has killed more than 200,000 of their fellow citizens and cost millions of jobs.
Over and over, Trump tried to control the conversation, interrupting Biden and repeatedly talking over the moderator, Chris Wallace of Fox News. The president tried to deflect tough lines of questioning - whether on his taxes or the pandemic - to deliver broadsides against Biden.
The president drew a lecture from Wallace, who pleaded with both men to stop interrupting. Biden tried to push back against Trump, sometimes looking right at the camera to directly address viewers rather than the president and snapping, "It's hard to get a word in with this clown."
But despite his efforts to dominate the discussion, Trump was frequently put on the defensive and tried to sidestep when he was asked if he was willing to condemn white supremacists and paramilitary groups.
"What do you want to call them? Give me a name. Give me a name," Trump said, before Wallace mentioned the far right, violent group known as the Proud Boys. Trump then pointedly did not condemn the group, instead saying, "Proud Boys, stand back, stand by,but I'll tell you what, somebody's got to do something about Antifa and the left because this is not right-wing problem. This is a left wing problem."
The vitriol exploded into the open when Biden attacked Trump's handling of the pandemic, saying that the president "waited and waited" to act when the virus reached America's shores and "still doesn't have a plan." Biden told Trump to "get out of your bunker and get out of the sand trap" and go in his golf cart to the Oval Office to come up with a bipartisan plan to save people.
Trump snarled a response, declaring that "I'll tell you Joe, you could never have done the job that we did. You don't have it in your blood."
"I know how to do the job," was the solemn response from Biden, who served eight years as Barack Obama's vice president.
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The pandemic's effects were in plain sight, with the candidates' lecterns spaced far apart, all of the guests in the small crowd tested and the traditional opening handshake scrapped. The men did not shake hands and, while neither candidate wore a mask to take the stage, their families did sport face coverings.
Trump struggled to define his ideas for replacing the Affordable Care Act on health care in the debate's early moments and defended his nomination of Amy Coney Barrett, declaring that "I was not elected for three years, I'm elected for four years."
"We won the election. Elections have consequences. We have the Senate. We have the White House and we have a phenomenal nominee, respected by all."
Trump criticized Biden over the former vice president's refusal to comment on whether he would try to expand the Supreme Court in retaliation if Barrett is confirmed to replace the late Justice Ruth Bader Ginsburg.
The president also refused anew to embrace the science of climate change.
As the conversation moved to race, Biden accused Trump of walking away from the American promise of equity for all and making a race-based appeal.
"This is a president who has used everything as a dog whistle to try to generate racist hatred, racist division," Biden said.
Recent months have seen major protests after the deaths of Black people at the hands of police. And Biden said there is systemic racist injustice in this country and while the vast majority of police officers are "decent, honorable men and women" there are "bad apples" and people have to be held accountable.
Trump in turn claimed that Biden's work on a federal crime bill treated the African American population "about as bad as anybody in this country." The president pivoted to his hardline focus on those protesting racial injustice and accused Biden of being afraid to use the words "law and order," out of fear of alienating the left.
"Violence is never appropriate," Biden said. "Peaceful protest is."
With just 35 days until the election, and early voting already underway in some states, Biden stepped onto the stage holding leads in the polls - significant in national surveys, close in some battleground states - and looking to expand his support among suburban voters, women and seniors. Surveys show the president has lost significant ground among those groups since 2016, but Biden faces his own questions encouraged by Trump's withering attacks.
-- The Associated Press contributed to this report.