Critics and even Trump's allies dismissed the notion as unserious and simply an attempt to distract from devastating economic news.
Trump's statement on Twitter comes as the United States is enduring the greatest crises of a generation: a coronavirus pandemic that has claimed more than 150,000 lives, a crippling recession sparked by the outbreak and nationwide protests against police violence and racism. On Thursday morning, the government reported the worst U.S. economic contraction since the Great Depression.
Trump, who opinion polls show losing ground to and trailing Democratic challenger and former Vice President Joe Biden, also said he would not trust the results of an election that included widespread mail voting - a measure that many observers see as critical given the coronavirus pandemic. Without evidence, he claimed that mail voting would be rife with fraud.
"With Universal Mail-In Voting (not Absentee Voting, which is good), 2020 will be the most INACCURATE & FRAUDULENT Election in history. It will be a great embarrassment to the USA," Trump wrote on Twitter. "Delay the Election until people can properly, securely and safely vote???"
The U.S. economy contracted by 32.9% in the second quarter, as the fast-spreading coronavirus sparked widespread lockdowns.
The United States has held elections for more than 200 years, including during the Civil War, the Great Depression and two world wars. Article II of the U.S. Constitution gives Congress the power to set the timing of elections, and the 20th Amendment ends a president and vice president's term in office on the Jan. 20 following a general election.
Multiple congressional Republicans - including Senate Majority Leader Mitch McConnell and top House of Representatives Republican Kevin McCarthy - rejected the idea.
"Never in the history of the federal elections have we ever not held an election and we should go forward with our election," said McCarthy. Senator Lindsey Graham, a Trump ally, said, "Delaying the election probably wouldn't be a good idea."
Democratic U.S. Representative Zoe Lofgren, who chairs the House committee overseeing election security, rejected any delay.
"Only Congress can change the date of our elections," Lofgren said in an email to Reuters. "Under no circumstances will we consider doing so to accommodate the President's inept and haphazard response to the coronavirus pandemic, or give credence to the lies and misinformation he spreads regarding the manner in which Americans can safely and securely cast their ballots."
'JUST CAN'T HELP HIMSELF'
Trump's tweet came without warning and surprised some White House staffers. The White House referred questions about the Tweet to Trump's re-election campaign, which in a statement said the president was simply raising a question.
"The President is just raising a question about the chaos Democrats have created with their insistence on all mail-in voting," said Hogan Gidley, the campaign's press secretary. "Universal mail-in voting invites chaos and severe delays in results."
A Republican close to the White House was stunned at the tweet, noting that it followed a period of stability in which Trump has stayed on message in response to advice from new campaign manager Bill Stepien and senior campaign manager Jason Miller.
"Obviously he just can't help himself. This is starting to look like a real campaign, and then he does this," the Republican source said. "It's awful. It's starting to look like he doesn't even want to win."
Trump had previously suggested he would not trust election results - complaints similar to those he raised going into the runup to the 2016 election - but had not so directly suggested changing the Nov. 3 date.
Trump without evidence has cast doubt on the legitimacy of mail-in ballots, which have been used in far greater numbers in primary elections amid the pandemic. He has also made unsubstantiated allegations that voting will be rigged and has refused to say he would accept official election results if he lost.
Many states earlier this year rescheduled primaries due to the fast-spreading coronavirus.
Ari Fleischer, who was White House press secretary under Republican President George W. Bush, said Trump should delete the tweet.
"This is not an idea anyone, especially POTUS, should float. Our democracy is based on elections in which everyone knows the rules and they apply to all," Fleischer said. "Mr. President - please don't even pretend to mess with this. It’s a harmful idea."
'DON'T LET IT HAPPEN'
Democrats, including Biden, have already begun preparations to protect voters and the election amid fears that Trump will try to interfere with the November election or dispute results - particularly if the final result is delayed by late-arriving mail-in ballots.
Polls have shown that U.S. registered voters oppose the idea of election delay. When Reuters/Ipsos in April asked voters if they thought the election should be rescheduled due to the coronavirus, 59% opposed the idea, including a majority of voters in each party.
A Biden campaign official said Trump's tweet was not a legitimate threat because he has no power to change the date of the election, and that it was an obvious ploy to distract from the awful GDP numbers.
"We're going to keep our eye on the ball," the Biden campaign official said.
"A sitting president is peddling lies and suggesting delaying the election to keep himself in power," Democratic Representative Dan Kildee wrote on Twitter. "Don't let it happen. Every American — Republican, Independent and Democrat — should be speaking out against this President's lawlessness and complete disregard of the Constitution."
Secretary of State Mike Pompeo sidestepped the issue at a Senate hearing, saying, "I'm not going to enter a legal judgment on that on the fly."
Dale Ho, director of the American Civil Liberties Union's voting rights project, likewise said Trump lacked the authority to reschedule an election.
"This is America," Ho said. "We are a democracy, not a dictatorship. The Constitution sets the date for the election in November. Nothing President Trump says, does, or tweets can change that fact."US stock indexes opened lower on Thursday as President Donald Trump raised the possibility of delaying the nation's November presidential election despite its date being enshrined in the US Constitution.The Dow Jones Industrial Average fell 172.15 points, or 0.65%, at the open to 26,367.42. The S&P 500 opened lower by 26.68 points, or 0.82%, at 3,231.76, while the Nasdaq Composite dropped 92.82 points, or 0.88%, to 10,450.12 at the opening bell.