President Donald Trump declared on Monday night he would "fight like hell" to hold on to the presidency and appealed to Republican lawmakers to reverse his election loss to Joe Biden when they convene this week to confirm the Electoral College vote.
Electoral voters won by President-elect Biden are "not gonna take this White House" he shouted as supporters cheered at an outdoor rally in Georgia.
Mr Trump's announced purpose for the trip was to boost Republican Senate candidates in Tuesday's runoff election, but he spent much of his speech complaining bitterly about his election loss — which he insists he won "by a lot".
Earlier, in Washington, he pressed Republican lawmakers to formally object on Wednesday at a joint session of Congress that is to confirm Mr Biden's victory in the Electoral College, itself a confirmation of Mr Biden's nationwide victory on November 3.
Though he got nothing but cheers on Monday night, Mr Trump's attempt to overturn the presidential election is splitting the Republican Party.
Some GOP lawmakers backing him 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 defence secretaries wrote in an op-ed that "the time for questioning the results has passed".
It is 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.
Mr Trump himself is whipping up crowds for a Wednesday rally near the White House.
Vice president Mike Pence, who is under pressure to tip the results for Mr 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," Mr Pence said while himself campaigning in Georgia ahead of Tuesday's runoff elections that will determine control of the Senate.
Mr Trump said in Georgia: "I hope that our great vice president comes through for us. He's a great guy. Of course, if he doesn't come through, I won't like him quite as much." He added: "No, Mike is a great guy."
One of the Georgia Republicans in Tuesday's runoff — senator Kelly Loeffler, who faces Democrat Raphael Warnock — told the crowd she will join senators formally objecting to Mr Biden's win.
The other Republican seeking reelection, David Perdue, who is running against Democrat Jon Ossoff, will not be eligible to vote.
Mr Trump repeated numerous times his claims of election fraud, which have been rejected by election officials — Republican as well as Democratic in state after state — and courts up to the US Supreme Court.
His former attorney general, William Barr, also has said there is no evidence of fraud that could change the election outcome.
Mr Biden, speaking at a drive-in rally in Atlanta earlier on Monday, said Mr 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 senator 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.
"It is the opposite of conservative; it is radical."
The US Chamber of Commerce, the giant lobbying organisation and virtual embodiment of the business establishment, said the electoral vote challenge "undermines our democracy and the rule of law and will only result in further division across our nation".
So far, Mr Trump has enlisted support from a dozen Republican senators and up to 100 House Republicans to challenge Mr Biden's 306-232 Electoral College win.
With Biden set to be inaugurated on January 20, Mr Trump is intensifying efforts to prevent the traditional transfer of power.
On a call disclosed on Sunday, he can be heard pressuring Georgia officials to "find" him more votes from the November 3 election he lost in that state.
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 Mr Trump's win, but Mr Biden, who presided at the time as the vice president, swiftly dismissed them to assert Mr Trump's victory.