(CNN) 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.
Track Electoral College votes, state by state
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 January 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, January 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.
While Trump has directed most of his Twitter ire at the courts and the GOP state officials who have properly certified their states' election results for Biden, he's now likely to focus on the upcoming vote counting in Congress. In a Fox News interview over the weekend, Trump claimed that "it's not over" and vowed to keep fighting to stay in office.
Minutes after California affirmed Biden's win with its vote, Trump tweeted that Attorney General William Barr would be leaving the administration later this month.
Trump's relationship with Barr has soured since the attorney general said after the election that the Justice Department had not uncovered evidence of widespread voter fraud and that the department under him had not disclosed an ongoing investigation into Biden's son, Hunter Biden, during the election, following Justice Department protocol. Joe Biden is not implicated.
Trump and his allies have suggested state legislatures should try to put forward alternate slates of electors who would go against the votes in their states.
No state legislature did so on Monday. But Republicans who had been named as electors for Trump in Pennsylvania, Georgia, Arizona and Wisconsin nevertheless met separately to cast symbolic votes for the President on Monday. Those votes have no validity under federal law, but GOP officials in the states said the Trump electors met because there are still ongoing legal challenges.
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 Michigan House and Senate offices were closed to the public Monday after "credible threats of violence" as the state's 16 electors prepare to cast their votes for president and vice president, a spokeswoman told CNN.
A Michigan House Republican was stripped of his committee assignments for the rest of the term after inciting violence around protests expected later Monday in Lansing. Michigan House Speaker Lee Chatfield, a Republican, and Speaker-elect Jason Wentworth released a statement on Monday condemning the comments of House Republican Rep. Gary Eisen, who said in a radio interview that he could not offer assurances there wouldn't be violence on Monday.
In a statement, Chatfield said the state will not change electors to give Trump the win, because doing so would "bring mutually assured destruction for every future election in regards to the Electoral College."
"I fear we'd lose our country forever" should Republicans switch the slate of electors, Chatfield added.
"I fought hard for President Trump," he wrote. "Nobody wanted him to win more than me. I think he's done an incredible job. But I love our republic, too. I can't fathom risking our norms, traditions and institutions to pass a resolution retroactively changing the electors for Trump, simply because some think there may have been enough widespread fraud to give him the win."
Monday's Electoral College vote is not the final step in the constitutional process of selecting a president. The votes cast on Monday are then sent to Congress, where they will be counted on January 6 in a joint session led by Vice President Mike Pence.
Some of Trump's staunchest House Republican allies are preparing for a floor fight when the votes are counted in Congress.
Lawmakers can dispute a state's election result when the votes are counted. But a challenge can be considered only if both a House member and a senator sign on to it. So far only House Republicans have said they will contest the results, although some GOP senators have suggested they are considering joining. Senate Republican leaders cautioned against such a move on Monday, however.
Even if a senator signs on to challenge the results, it's only delaying the inevitable. In that case, the House and Senate separately debate the matter for two hours and vote on it. Democrats control the House, and enough GOP senators have already said they reject Trump's claims of fraud that a challenge would not succeed there either.
After the state electors cast their ballots, the results are certified and sent to Congress, the National Archives and the courts.
As laid out in the Constitution, each state sets its own rules for how electors meet and vote. At least one state -- Nevada -- met virtually due to the pandemic.
Electors are picked by the state parties before the November election. Federal lawmakers are not allowed to be electors, but the slates usually include local officials and party alumni. In New York, for instance, former President Bill Clinton and former Secretary of State Hillary Clinton cast electoral votes for Biden.
In Florida, Republican state Senate President Wilton Simpson, who was a state elector, tested positive for Covid-19 on Sunday night. As a result, he did not participate in the Electoral College vote Monday and an alternate took his place to cast a ballot for Trump.
One of Michigan's 16 electors was not in attendance for the vote, so electors voted on a replacement to fill the vacancy prior to casting their vote for Biden.