Senator Mitt Romney of Utah, the 2012 Republican presidential nominee, said that President Trump “was wrong to say the election was rigged, corrupt or stolen” and that doing so “damages the cause of freedom here and around the world, weakens the institutions that lie at the foundation of the Republic and recklessly inflames destructive and dangerous passions.”
The Republican Senator Pat Toomey of Pennsylvania, a state that could send Mr. Biden to the White House but where Mr. Trump has baselessly claimed there had been fraud, said, “The president’s allegations of large-scale fraud and theft of the election are just not substantiated.”
And Gov. Larry Hogan of Maryland, another Republican, wrote that there was “no defense” for Mr. Trump’s comments “undermining our democratic process.”
A growing number of Republicans were speaking out against Mr. Trump’s false allegations that the election had been rigged against him, especially after he delivered a rambling jeremiad filled with conspiracy theories in the White House briefing room on Thursday.
“I saw the president’s speech last night,” Mr. Toomey said Friday morning. “It was very hard to watch.”
A few hours later, Mr. Romney, a semi-frequent Trump critic, wrote on Twitter that while the president was “within his rights to request recounts” and to call out “irregularities where evidence exists,” his statements were reckless.
Some Trump allies did rally around the president. Senator Lindsey Graham of South Carolina appeared on Fox News on Thursday to defend Mr. Trump’s claims of fraud. “I don’t trust Philadelphia,” he said, referring to the city where Mr. Biden has gotten more than 80 percent of the vote. He offered no evidence for his statement.
Senator Ted Cruz of Texas also appeared on the network and accused Democrats of trying to steal the election. He also offered no evidence to back his assertion.
Many prominent Republican lawmakers remained silent, declining to cross Mr. Trump over the results of an election that was slipping away from the incumbent.
At a news conference on Thursday night in Atlanta with Donald Trump Jr., in which Republican supporters chanted “stop the steal,” Representative Doug Collins, a Georgia congressman who just lost a bid for Senate, suggested without evidence that something was awry in the election. “Transparency only seems to be good when the Democrats like the transparency, and the media are willing to go along with it,” he said.
And Tommy Tuberville, a senator-elect from Alabama and a former Auburn University football coach, echoed the president on Twitter.
“The election results are out of control,” Mr. Tuberville wrote. “It’s like the whistle has blown, the game is over, and the players have gone home, but the referees are suddenly adding touchdowns to the other team’s side of the scoreboard.”
Representative Kevin McCarthy of California, the Republican leader, at first sidestepped questions on Wednesday about whether he agreed with Mr. Trump that election officials should halt their tabulations.
But by Thursday evening, he grew more vocal, writing in a tweet: “Republicans will not be silenced. We demand transparency. We demand accuracy. And we demand that the legal votes be protected.”