WASHINGTON — Joe Biden says his chief worry is that President Donald Trump will attempt to "steal" the November election, and the Democratic challenger says he's even considered the possibility that the Republican incumbent would refuse to leave the White House should he lose.

"My single greatest concern: This president's going to try and steal this election," Biden said on "The Daily Show with Trevor Noah," which aired Wednesday night. "This is a guy who said all mail-in ballots are fraudulent, voting by mail, while he sits behind the desk in the Oval Office and writes his mail-in ballot to vote in the primary."

Biden was asked whether he's considered what would happen if Trump refused to vacate the White House in the event he wasn't reelected. "I have," Biden said, before suggesting that the military could step in to ensure a peaceful transition of power. 

""I am absolutely convinced they will escort him from the White House with great dispatch," the former vice president said. 

Biden's comments come as Trump has intensified his claim that absentee voting, which many states are expanding to avoid large crowds at polling places during the coronavirus pandemic, increases the possibility of fraud. There is little evidence to support that assertion; Trump himself has voted by mail in the past. 

A chaotic Tuesday primary in Georgia, where there were problems with voting machines and long lines, may foreshadow a messy November election. 

Trump on Thursday planned to resume in-person fundraising events after a three-month hiatus as his campaign tries to maintain a steep cash advantage over Biden. The president was traveling to Dallas to raise more than $10 million for his campaign and the Republican Party. He scheduled another event Saturday at his New Jersey golf course.

Biden has previously suggested that Trump's opposition to mail-in ballots could upend the presidential election. "This president, mark my words, I think he's going to try to kick back the election somehow, come up with a rationale why it can't be held," he said during an April fundraiser. 

"He's already trying to undermine the election with false claims of voter fraud and threatening to block essential COVID assistance if any extra funds go to the U.S. Postal Service," Biden said at the time. "What in God's name was that about other than trying to let the word out that he's going to do all that he can to make it very hard for people to vote."

During the "Daily Show" interview, Biden said that more than 20 states had passed 80-plus pieces of legislation "making it harder for people vote." He said his campaign was assembling a team of lawyers to observe balloting in "every district in the country."

Also Wednesday, Biden acknowledged during a virtual NAACP forum that questions raised about his support for the 1994 crime bill are "legitimate." Biden helped write the tough-on-crime bill when he was a Delaware senator. Critics say it contributed to the mass incarceration of racial minorities.

Black voters remain key to Democrats' chances in the general election. Biden has engaged in a concerted outreach effort to the African American community, and he has released a plan focused on black economic mobility and racial disparities in health care and education systems. 

"Watch what I do," he said during the forum. "Judge me based on what I do, what I say and to whom I say it."