President Trump drew immediate rebukes from Republicans and Democrats alike on Thursday after floating the prospect of delaying the November election and claiming without evidence that widespread mail balloting would be a “catastrophic disaster” leading to fraudulent results.

The suggestion represented Trump’s latest, and most dramatic, attempt to undermine public faith in U.S. elections, which have grown more regular as polls have shown his political fortunes declining. The president has attacked mail voting nearly 70 times since late March in interviews, remarks and tweets, including at least 17 times this month, according to a tally by The Washington Post.

Thursday’s tweet came on the heels of a devastating report showing that the economy shrank nearly 10 percent from April through June, the largest quarterly decline since the government began publishing such data 70 years ago.

Senior Republicans, who often refuse to weigh in on President Trump’s controversial tweets, overwhelmingly rejected his idea Thursday that the election be postponed because of the risk of fraud.

“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,” said Senate Majority Leader Mitch McConnell (R-Ky.) in a television interview with Georgia NBC affiliate WNKY. “We’ll find a way to do that again this Nov. 3.”

Trump gave no indication that he will push for the date change, or that he thinks he has the power to do so.

“With Universal Mail-In Voting (not Absentee Voting, which is good), 2020 will be the most INACCURATE & FRAUDULENT Election in history,” the president tweeted Thursday morning. “It will be a great embarrassment to the USA. Delay the Election until people can properly, securely and safely vote???”

The U.S. Constitution gives the power to regulate the “time, place and manner” of general elections to Congress, while states control the dates of primary elections. Nowhere is the president granted such power.

In addition, the Constitution spells out a hard end to a president’s and vice president’s terms on Jan. 20 in the year following a presidential election, whether an election is held or not.

“The President has no power to change the date of the election,” said Richard L. Hasen, a law professor at the University of California at Irvine. “This is yet another statement by the President which undermines voter confidence and that seeks without evidence to undermine the legitimacy of voting by mail.”

Some Republicans — and many Democrats — expressed alarm at the president’s apparent disregard for the limits of his power.

“Election Day is and will be Nov 3, 2020,” said Republican Ari Fleischer, a former press secretary to George W. Bush. “Mr. President — please don’t even pretend to mess with this. It’s a harmful idea.”

Added Sen. John Barrasso (R-Wyo.) in a Fox News interview Thursday morning: “We will not delay the election.” Sen. Marco Rubio (R-Fla.), Sen. Lindsey O. Graham (R-S.C.) and House Minority Leader Kevin McCarthy (R-Calif.) weighed in similarly.

House Speaker Nancy Pelosi (D-Calif.) simply tweeted the relevant passage from the Constitution granting Congress the power to set election dates.

Other Democrats suggested that Trump’s suggestion reflected a realization that he could lose to presumptive Democratic nominee Joe Biden, who has been leading in national and many battleground state polls.

“Donald Trump is terrified,” tweeted Sen. Kamala D. Harris (D-Calif.), who is among those being considered as a running mate for Biden. “He knows he’s going to lose to @JoeBiden. It will require every single one of us to make that happen. We will see you at the ballot box on November 3rd, @realDonaldTrump.”

Some Democrats used the occasion to promote how-to instructions on mail balloting.

“President Trump is talking about delaying the November election because he is afraid of people voting by mail,” Rep. Donna Shalala (D-Fla.) said in a tweet in which she included a link to a Florida government website with instructions on how to do so. “You know what to do,” she added.

U.S. Rep. James E. Clyburn (D-S.C.) called Trump’s tweet “despicable,” especially because it came on the day of civil rights icon John Lewis’s funeral.

“Americans will rise up & continue John’s fight for unfettered access to the ballot box,” Clyburn tweeted. “Our voices will not be silenced.”

Trump appeared unfazed by the criticism, even “pinning” the message at the top of his Twitter feed to elevate its stature. But several Trump advisers said no internal discussions are underway within the White House about moving the election. “He is just trolling,” said one senior adviser who requested anonymity to speak candidly. Another said the tweet caught aides by surprise.

Ronna McDaniel, chairwoman of the Republican National Committee, said on Fox Business that “obviously” the president understands that he doesn’t have the authority to move the election. She said Trump is simply objecting to Democratic efforts to “systematically take away safeguards to election integrity” by expanding mail-in balloting.

“We need to get this fixed and it’s going to cause problems in November if we don’t pay attention now,” she said.

As more states have turned to mail-in voting in response the pandemic, Trump has repeatedly sought to undermine the method, often with unsubstantiated claims. He has attacked mail voting nearly 70 times since late March in interviews, remarks and tweets, including at least 17 times this month, according to a tally by The Washington Post.

A Department of Justice spokeswoman declined to comment on Trump’s tweet. Earlier this week at a House Judiciary Committee hearing, however, Attorney General William P. Barr told Rep. Cedric L. Richmond (D-La.) he had not studied the question of whether the president could move the election date.

“I’ve never been asked the question before, I’ve never looked into it,” Barr said.

Biden suggested in April that Trump might try to move the election date. At the time, Trump campaign spokesman Tim Murtaugh accused Biden of “incoherent, conspiracy-theory ramblings” and said “President Trump has been clear that the election will happen on Nov. 3.”

Another Trump spokesman, Hogan Gidley, said in a statement that the president was merely “raising a question about the chaos Democrats have created with their insistence on all mail-in voting.”

In fact, most Democrats are pushing for mail balloting in addition to early in-person and Election Day voting, because many voters are more comfortable casting their ballots in person.

Trump has argued that mail-in voting tends to hurt Republicans at the ballot box.

A Washington Post-ABC News poll conducted this month shows that 51 percent of Democrats prefer voting by mail this fall, compared to 20 percent of Republicans. However, a recent study by Stanford University researchers found no partisan impact of expanding voting by mail.

At the congressional hearing, Barr repeated his concern that he felt there was a “high risk” mail-in voting would lead to fraud, but said he did not believe the election would be rigged — seeming to break with Trump.

“I have no reason to think it will be,” Barr said.

Even if Congress voted to delay the general election, the electoral college is still required to elect a president under federal law. If lawmakers changed that too, Trump and Vice President Pence would still be required to leave office by noon on Jan. 20. With no successor, the speaker of the House of Representatives, currently Pelosi, would be next in line.

Josh Dawsey, Elise Viebeck, Scott Clement, Matt Zapotosky, Erica Werner, Seung Min Kim and Devlin Barrett contributed to this report.