Transcript for President Trump casts doubt on November election
And just hours before the service began, president trump, who did not attend, did send out a tweet suggesting that election day be delayed. It set off a firestorm, even Republican leaders jumping in and quickly to try to put this to rest. Here's Terry Moran tonight on that. Reporter: No president has ever said anything like it. But president trump, behind in the polls, with a cratering economy and a pandemic out of com, tweeting today -- "With universal mail-in voting, 2020 will be the most inaccurate and fraudulent election in history. It will be a great embarrassment to the usa. Delay the election until people can properly, securely and safely vote?" Later, the president tried to explain what he meant. Do I want to see a date change? No. But I don't want to see a crooked election. This election will be the most rigged election in history if that happens. Reporter: That's a flip-flop. In April, trump said this. I never even thought of changing the date of the election. Why would I do that? November 3rd. It's a good number. No, I look forward to that election. Reporter: Trump's statement today about delaying an American election was shot down immediately by Democrats and Republicans. Senate majority leader Mitch Mcconnell, in an interview in Kentucky. Never in the history of the country, through wars, depressions and the civil war, have we ever not had a federally scheduled election on time. Reporter: But Joe Biden has been warning for weeks that trump might try to use the pandemic to delay or delegitimize the election. It's my greatest concern. My single greatest concern. This president's going to try to steal this election. This is a guy who said all mail-in ballots are fraudulent. Voting by mail. While he sets behind a desk in the oval office and writes his mail-in ballot to vote in a primary. And Terry Moran with us tonight. I know amid all this talk about mail-in bat ballots and election security, but ABC news did reach to election officials in all 50 states, Democrats and Republicans, about whether they're concerned about mail-in voting. Reporter: That's right, David. We've heard from 27 of those top election officials across the country and not one of them, Republican or Democrat, has expressed any concern that mail-in voting would cause any significant fraud in their states. It is also worth noting, David, that neither the constitution nor federal law gives the president any power to change the election or to extend his term. David? Terry Moran with us tonight, as well. Terry, thank you. Of course, it's hard to predict where we'll be with this pandemic once election day arrives, but tonight, what we do know is, the numbers are worsening right now in several states.
This transcript has been automatically generated and may not be 100% accurate.