WASHINGTON — Joe Biden was once again declared the winner of the presidential election Monday after members of the Electoral College gathered in all 50 states and the District of Columbia to cast their ballots.

It's a constitutionally mandated ritual that's typically no more than a curious afterthought following a presidential election, but the ceremonial vote took on newfound significance this year as President Donald Trump and his GOP allies made unprecedented efforts to subvert the popular will of the voters and overturn Biden's November victory.

The vote finally shook loose statements acknowledging Biden's win from previously reluctant Republicans, but Republican-appointed electors in several states gathered to hold symbolic votes for Trump — while a retiring Republican congressman announcing he was leaving the party over his colleagues' unwillingness to move on.

President-elect Biden pointedly criticized President Trump on Monday for threatening core principles of democracy even as he told Americans that their form of self-government ultimately “prevailed.”

It came after the Electoral College decisively confirmed Biden as the next US president, ratifying his November victory in an authoritative state-by-state repudiation of President Donald Trump’s refusal to concede that he lost.

The presidential electors gave Biden a solid majority of 306 electoral votes to Trump's 232 — 36 votes over the 270 needed to win. It is the same margin that Trump bragged was a landslide when he won the White House four years ago.

"Once again in America, the rule of law, our Constitution, and the will of the people have prevailed. Our democracy — pushed, tested, threatened — proved to be resilient, true, and strong,” Biden said in an evening speech in which he stressed the size of his win and the record 81 million people who voted for him.

He renewed his campaign promise to be a president for all Americans, whether they voted for him or not, and said the country has hard work ahead on the virus and economy.

The voting kicked off shortly after 10 a.m. ET, with Vermont's three electors casting the first votes for Biden. All of the votes went as expected — no states had any so-called "faithless electors" break from the popular vote.

And all the battleground states that Trump has sought to overturn — Nevada, Georgia, Pennsylvania, Arizona, Michigan and Wisconsin — cast their electoral votes for Biden. California's 55 electors put Biden over the 270 Electoral College votes needed to become president shortly after 5 p.m. ET.

The Electoral College votes will next be sent to Congress to be counted formally next month. A group of House Republicans have vowed to object to the results in the key states, but they can do little more than delay the process and force a prolonged debate during the joint session of Congress, scheduled for Jan. 6, when the vote is finalized.

Trump has continued to spread false claims of widespread fraud despite courts in all of the battleground states rejecting his campaign's challenges to the election. The Supreme Court dealt the final blow against his efforts to overturn the election result late Friday, dismissing a case brought by the Texas attorney general that sought to disenfranchise millions of voters in four states.

Wisconsin's Supreme Court denied yet another challenge from Trump's campaign on Monday, just before the state's electors were scheduled to meet and cast their votes for Biden.

Biden spoke Monday evening in praise of the state and local officials who "could not and would not give credence to what they knew was not true." He charged that the Republican efforts to overturn the result represented an "unprecedented assault on our democracy," while noting that "every single avenue was made available to President Trump to contest the results."

"Respecting the will of the people is at the heart of our democracy, even if we find those results hard to accept," Biden said. "We the people voted. Faith in our institutions held. The integrity of our elections remains intact. And now it's time to turn the page as we've done throughout our history, to unite to heal."

Trump's baseless attacks on the election result — and the widespread support of the President's efforts from Republican leaders in Congress — prompted Rep. Paul Mitchell of Michigan, who didn't run for reelection this year, to say in a letter to House Minority Leader Kevin McCarthy and Republican National Committee Chairwoman Ronna McDaniel that he was withdrawing from the party.

"This party has to stand up for democracy first, for our Constitution first, and not political considerations," Mitchell told CNN's Jake Tapper on Monday. "Not to protect a candidate. Not simply for raw political power, and that's what I feel is going on, and I've had enough."

In Congress, most Republicans declined to say that Biden is the President-elect before Monday's vote, despite a decisive Electoral College victory and baseless claims of voter fraud being thrown out repeatedly in the courts. A majority of House Republicans, including McCarthy, signed on to the Texas lawsuit seeking to overturn the results in four states.

Some key Senate Republicans finally acknowledged Biden as President-elect as the Electoral College voting wrapped up on Monday. Sen. John Cornyn, a Texas Republican in Senate leadership, said "yes" when asked if he would now call Biden President-elect, barring any additional litigation between now and Inauguration Day, Jan. 20.

"I think he's President-elect subject to whatever additional litigation is ongoing," Cornyn said, adding it would be a "bad mistake" for House Republicans to object to the results of the Electoral College vote.

Senate Majority Whip John Thune, a South Dakota Republican, said Monday that Biden is President-elect once he crosses 270 electoral votes. "Once the Electoral College settles the issue today, it's time for everybody to move on," Thune said.

The heightened attention to Monday's Electoral College voting prompted several states to put security protocols in place due to concerns over safety, threats and protests.

In Arizona, the electors met at an undisclosed location, according to the public information office for the secretary of state. And in Wisconsin, electors were told to use an unmarked entrance with police escort, according to one of the electors.

"For elections officials in Arizona, this is the final step in our process. And one that is usually conducted with much pomp and circumstance, with the reverence it deserves for its place in history," Arizona Secretary of State Katie Hobbs, a Democrat, said during the state's gathering.

"But this year's proceeding, which occurs only once every four years, has unfortunately had an artificial shadow cast over it in the form of baseless accusations of misconduct and fraud, for which no proof has been provided, and which court after court has dismissed as unfounded. And this fabrication of misdeed, leveled against everyone from poll workers to me and my office, has led to threats of violence against me, my office and those in this room today."

The president had grown increasingly disappointed with the size of “Stop the Steal” rallies across the nation as well as efforts for the GOP to field its own slates of electors in states.

A presidential wish for a fierce administration defense led to TV appearances early Monday by Stephen Miller, one of his most ferocious advocates, to try to downplay the importance of the Electoral College vote and suggest that Trump’s legal challenges would continue all the way to Inauguration Day on Jan. 20.

Former President Bill Clinton and former Secretary of State Hillary Clinton, whom Trump defeated four years ago, were among New York's 29 electors for Biden and Harris.

In New Hampshire, before the state’s four electors voted for Biden at the State House in Concord, 13-year-old Brayden Harrington led the group in the Pledge of Allegiance. He had delivered a moving speech at the Democratic National Convention in August about the struggle with stuttering he shares with Biden. — Agencies