Breaking with President Trump’s drive to overturn his election loss, Senator Mitch McConnell of Kentucky, the most powerful Republican in Congress, said on Tuesday that the Electoral College’s vote had removed any doubt that Joseph R. Biden Jr. would be the next president.
“Many of us hoped that the presidential election would yield a different result, but our system of government has processes to determine who will be sworn in on Jan. 20,” Mr. McConnell, the majority leader, said in a speech on the Senate floor, after weeks of declining to recognize Mr. Biden’s win. “The Electoral College has spoken. So today, I want to congratulate President-elect Joe Biden.”
He also congratulated Senator Kamala Harris of California, referring to her as the vice president-elect.
“Beyond our differences, all Americans can take pride that our nation has a female vice president-elect for the very first time,” Mr. McConnell said.
The remarks were a decisive shift for Mr. McConnell and came hours after members of his leadership team in the Senate, and even the chamber’s chaplain, began softening the ground by congratulating Mr. Biden Monday evening and Tuesday morning.
Though he never repeated them, Mr. McConnell had allowed Mr. Trump’s baseless allegations of widespread voting fraud or fantastical claims that he had won the election by a wide margin to circulate unchecked for more than a month. Allies insisted privately that he would ultimately honor the election results, but did not want to stoke a year-end conflict with the president that could hurt the party’s chances in two Georgia Senate runoffs and imperil must-pass legislation.
Nevertheless, his decision to break with the president now further exposed the divisions within the Republican Party and its representatives in Congress. Polls suggest a clear majority of Republicans believe Mr. Trump’s fabrication that the election was fraudulent, and they are likely to follow the president’s words, not those of Mr. McConnell. And many of the president’s allies in the House continue to support his challenges to the results, with more than 60 percent of them signing on last week to a legal brief endorsing the failed effort by Texas to overturn results in key battleground states.
Mr. Trump showed no signs of backing down, declaring on Twitter just after Mr. McConnell spoke: “tremendous evidence pouring in on voter fraud.”
“There has never been anything like this in our country!” he added. There has been no evidence of the kind of broad-based fraud Mr. Trump insists occurred.
He also shared a Breitbart news article about Representative Mo Brooks of Alabama, who is plotting one final challenge to the results for Jan. 6, when Congress will meet in joint session to ratify the Electoral College’s decision. Mr. McConnell’s unequivocal embrace of the Electoral College results likely makes what was already a long shot even more difficult.
But others in the party fear Mr. Trump’s continued defiance of democratic norms, and acquiescence by much of the party, will do lasting damage not just to the G.O.P. but the country. One of them, Representative Paul Mitchell of Michigan, who is retiring, went as far as to quit the party on Monday in protest.
In his remarks on Tuesday, Mr. McConnell did not directly address the president’s attacks on the election or party officials who ran it in key states that he lost by clear margins. Instead, he effusively praised the president for his four years of service, spending several minutes listing what he said were important achievements in domestic and foreign policy before he ever mentioned Mr. Biden’s name.
“The outsider who swore he would shake up Washington and lead our country to new accomplishments at home and abroad proceeded to do exactly that,” he said.
Following Mr. McConnell on the chamber floor, Senator Chuck Schumer of New York, the Democratic leader, urged Mr. Trump to “take his cue” from Mr. McConnell and publicly accept Biden as next president with “a modicum of grace and dignity.”