WASHINGTON (AP) — With mounting desperation, President Donald Trump appealed to Republican lawmakers Monday to reverse his election loss to Joe Biden when Congress convenes for a joint session this week to confirm the Electoral College vote.

Trump's unprecedented attempt to overturn the presidential election i s splitting the Republican Party. Some GOP lawmakers backing Trump are rushing ahead, despite an outpouring of condemnation from current and former party officials warning the effort is undermining Americans’ faith in democracy. All 10 living former defense secretaries wrote in an op-ed article that "the time for questioning the results has passed."

It’s unclear the extent to which GOP leaders in Congress will be able to control Wednesday’s joint session, which could drag into the night, though the challenges to the election are all but certain to fail. Trump himself is whipping up crowds for a Wednesday rally near the White House.

Trump's allies are taking up his unfounded claims of voter fraud. But according to a consensus of election officials in the states he's disputing — as well his former Attorney General William Barr — there is no evidence of fraud that could change the election outcome. Officials who have control over elections in their states, including battlegrounds Biden won, have certified those results as valid.

Of the more than 50 lawsuits the president and his allies have filed challenging results, nearly all have been dismissed or dropped. He’s also lost twice at the U.S. Supreme Court.

The effort to keep Trump in office is being led by Sens. Josh Hawley of Missouri and Ted Cruz of Texas, along with rank-and-file House members, some on the party's fringe.

“Just got off the phone with @realDonaldTrump,” tweeted newly elected Rep. Marjorie Taylor Greene of Georgia, who is aligned with a conspiracy group backing Trump.

“He wants you to call your Rep & Senators TODAY, ALL DAY!" she tweeted Monday, . "Don’t let Republicans be the Surrender Caucus!” She later said she joined the president on Air Force One as he traveled to Georgia

Senate Majority Leader Mitch McConnell has tried to prevent his party from engaging in this battle, which could help define the GOP in the post-Trump era. House Minority Leader Kevin McCarthy, a Trump ally, has declined to say much publicly on it.

Both Hawley and Cruz are potential 2024 presidential contenders, vying for Trump's base of supporters. Vice President Mike Pence, who is under pressure to tip the results for Trump, will be closely watched as he presides in a ceremonial role over Wednesday's joint session.

"I promise you this: On Wednesday, we’ll have our day in Congress,” Pence said while campaigning in Georgia for Republicans ahead of Tuesday's runoff elections that will determine control of the Senate.

One of those Georgia Republicans, Sen. Kelly Loeffler who faces Democrat Raphael Warnock, announced she will object to Biden's win. The other Republican seeking re-election, David Perdue, who is running against Democrat Jon Ossoff, will not be eligible to vote Wednesday in the Senate.

Biden, speaking at a drive-in rally in Atlanta, said Trump “spends more time whining and complaining” than he does working on solving the coronavirus pandemic. He added dismissively: “I don’t know why he still wants the job — he doesn’t want to do the work.”

During the day Monday, more current and former GOP officials rebuked the effort to upend the election.

Former three-term Sen. John Danforth of Missouri said in a stinging statement: “Lending credence to Trump’s false claim that the election was stolen is a highly destructive attack." He said, "It is the opposite of conservative; it is radical."

Two current Republican senators, Rob Portman of Ohio and Mike Lee of Utah, joined the growing number who now oppose the legislators' challenge.

Portman said in a statement, “I cannot support allowing Congress to thwart the will of the voters.”

The U.S. Chamber of Commerce, the giant lobbying organization and virtual embodiment of the business establishment, said that the electoral vote challenge “undermines our democracy and the rule of law and will only result in further division across our nation.”

Massachusetts GOP Gov. Charlie Baker said at a press conference that Biden "won the election fair and square.”

So far, Trump has enlisted support from a dozen Republican senators and up to 100 House Republicans to challenge Biden’s 306-232 Electoral College win. Cruz convened a private strategy call late Monday with some of the House and Senate Republicans involved.

With Biden set to be inaugurated Jan. 20, Trump is intensifying efforts to prevent the traditional transfer of power. On a call disclosed Sunday, he can be heard pressuring Georgia officials to “find” him more votes from the Nov. 3 election he lost in that state.

Speaker Nancy Pelosi, who convened a private call of House Democrats on Monday, said in a letter to colleagues their job now “is to convince more of the American people to trust in our democratic system.”

The challenge to the presidential election is on a scale unseen since the aftermath of the Civil War, though the typically routine process of confirming Electoral College votes has been hit with brief objections before. In 2017, several House Democrats challenged Trump’s win, but Biden, who presided at the time as the vice president, swiftly dismissed them to assert Trump’s victory.

States run their own elections, and Congress has been loath to interfere.

“The 2020 election is over,” said a statement Sunday from a bipartisan group of 10 senators, including Republicans Susan Collins of Maine, Lisa Murkowski of Alaska, Bill Cassidy of Louisiana and Mitt Romney of Utah.

Republican Sen. Tom Cotton of Arkansas, another potential 2024 presidential hopeful, announced he, too, would not oppose the counting of certified electoral votes.

A range of Republican officials, including Gov. Larry Hogan of Maryland; Rep. Liz Cheney of Wyoming, the third-ranking House GOP leader; and former House Speaker Paul Ryan, have criticized the GOP efforts to overturn the election.

Hawley defended his actions in a lengthy email over the weekend to colleagues, saying his Missouri constituents have been “loud and clear” in insisting Biden's defeat of Trump was unfair.

Cruz's coalition of 11 Republican senators vows to reject the Electoral College tallies unless Congress launches a commission to immediately conduct an audit of the election results. Congress is unlikely to agree to that.

The group, which presented no new evidence of election problems, includes Sens. Ron Johnson of Wisconsin, James Lankford of Oklahoma, Steve Daines of Montana, John Kennedy of Louisiana, Marsha Blackburn of Tennessee, Mike Braun of Indiana, Cynthia Lummis of Wyoming, Roger Marshall of Kansas, Bill Hagerty of Tennessee and Tommy Tuberville of Alabama.

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Associated Press writers Bill Barrow in Atlanta, Steve LeBlanc in Cambridge, Massachusetts, Jim Salter in O’Fallon, Missouri, Alan Fram in Washington and Tali Arbel of the Technology Team. contributed.