Electors in Pennsylvania, one of the election’s most heavily litigated battleground states, gathered for socially-distanced proceedings in Harrisburg at noon where Rich Fitzgerald of Allegheny County, chief tally, officially certified Pennsylvania’s 20 Electoral College votes for Biden and Harris at 12:45 p.m.

Pennsylvania Secretary of State Kathy Boockvar, a Democrat, appeared to give a nod to Republicans in her state who were vocal in challenging the outcome of the 2020 election when opening the meeting by quoting the late President George H.W. Bush -- the last one-term president prior to Trump.

"As President George Herbert Walker Bush eloquently said after the 1992 election, 'The people have spoken.' And we respect the majesty of the democratic system, your participation today in this Electoral College proves once again, the durability of our constitution and the majesty of our democracy," she said.

Malcolm Kenyatta -- a 30-year-old, gay, Black man who made his mark on the national stage as one of a group of young Democratic National Convention keynote speakers whom the party identified as "diverse voices from the next generation of party leaders” -- offered the resolution for the balloting for the President and Vice President of United States.

As the electors’ votes were certified, the state’s GOP appeared to lean into political theater by announcing that they cast a conditional vote for Trump and Vice President Mike Mike Pence. The move does not affect the outcome of the electors meeting, nor does it challenge Biden as the recipient of the state’s electoral votes.

"We took this procedural vote to preserve any legal claims that may be presented going forward. This was in no way an effort to usurp or contest the will of the Pennsylvania voters," Bernie Comfort, the vice chairwoman of the Pennsylvania GOP, who is also the Pennsylvania chair of the Trump campaign, said in a statement.

-ABC News' Alisa Wiersema

With the president and his allies continuing their pressure campaign to overturn the election, some of the battleground states where Biden won are taking additional security precautions to safeguard their electors meeting Monday.

In Georgia, a spokesperson for Van R. Johnson, the mayor of Savannah and an elector for Biden this year, confirmed that he has additional security measures in place today as a "precautionary measure," without providing details on any specifics. The measures were first reported by the New York Times.

The Democratic Party of Georgia would only say that they've taken "every measure" to ensure the safety of their electors.

In Michigan, where protests are planned outside the state Capitol, electors were promised police escorts, ABC News confirmed.

Late Sunday night, officials announced that the state legislature's office buildings will be closed to the public due to "credible threats of violence." The decision to close the state House and Senate offices while the presidential electors convene to cast their votes for Biden came from a recommendation from law enforcement. It was not motivated by anticipated protests outside the capitol, according to a statement from Amber McCann, a spokesperson for Senate Majority Leader Mike Shirkey.

In Arizona, the secretary of state’s office is not publicizing the location of their meeting due to “security reasons,” according to a spokesperson.

-ABC News' Kendall Karson, Alisa Wiersema, Quinn Scanlan and Meg Cunningham

The normally conservative-leaning Wisconsin Supreme Court has ruled 4-3 against President Trump, rejecting his effort to challenge the state’s election recount, saying he tried to throw the challenge flag "long after the last play, or even the last game."

"The challenge … is meritless on its face," wrote Justice Brian Hagedorn, who spent years as the chief counsel to Republican Gov. Scott Walker, in the majority opinion.

The court’s majority takes issue with a number of the complaints leveled by the Trump campaign about how mail-in ballots were collected. But the four justices ultimately agreed that any issues should have been raised well before the election, not after the president lost.

"The issues raised in this case, had they been pressed earlier, could have been resolved long before the election," Hagedorn wrote. "The Campaign's delay in raising these issues was unreasonable in the extreme."

Chief Justice Patience Drake Roggensack authored the dissent, which argued that the court’s majority hid behind the argument that Trump’s filing came too late, in order not to address concerns the president raised about the way ballots were collected. Roggensack said there were “numerous problems that will be repeated again and again, until this court has the courage to correct them.”

Biden won Wisconsin by more than 20,000 votes.

-ABC News' Matthew Mosk, Alex Hosenball and Soo Rin Kim

In a video meeting with little fanfare, Nevada's six Democratic electors cast votes for Biden and Vice President-elect Kamala Harris -- the first electors in the country to cast their votes. Silent clapping ensued at the conclusion of the meeting.

Prior to the electors casting their votes for Biden and Harris, deputy Secretary of State Mark Wlaschin reminded the electors they are legally required to vote for the Democratic ticket as it clinched more votes in the state, and if they did not, they would be replaced. At the start of the meeting, they signed a pledge agreeing to vote for the candidates who received the highest number of votes in the general election.

"In addition to this pledge, state law requires you to vote for Joseph R. Biden for president, and Kamala D. Harris for vice president. If you vote for any other person, or leave your ballot blank, neither of your ballots will be accepted, and your position as Presidential Elector will be vacated, and an alternate would be selected to fill your vacancy," Wlaschin said.

Thirty-three states -- including Nevada -- and Washington, D.C., require electors to keep their pledge. In at least five states, penalties exist for defiant votes, while over a dozen states cancel and replace the rogue elector.

More laws are likely to be enacted over the coming years to require electors to follow the popular vote after the U.S. Supreme Court ruled earlier in the year that it is constitutionally permissible to bind electors to vote for the popular vote winner.

While experts aren't anticipating any spectacles with "faithless" electors this year, ten members of the Electoral College voted or attempted to vote against the candidate that won in their state in 2016.

-ABC News' Kendall Karson