oleksii arseniuk/iStockBY: KENDALL KARSON, ABC NEWS

(WASHINGTON) — The 538 members of the Electoral College are set to cast votes for president and vice president on Monday — marking another step toward making President-elect Joe Biden’s victory official.

The vote is traditionally little more than a formality. But this year, with President Donald Trump resisting his defeat at every turn and waging long-shot legal battles with baseless claims of widespread fraud, the meeting comes at a tense and fragile moment for the country’s democratic institutions and is one that will happen irrespective of the outgoing president’s efforts to subvert the electoral process.

The electors will seal Biden as the winner ahead of his swearing in at the inauguration on Jan. 20. His margin of victory in the Electoral College is expected to be 306 votes to Trump’s 232, if there are no surprises.

Here’s a rundown of what to expect on Monday:

What is the Electoral College?

While the public elects members of Congress, governors, state legislators, mayors and other local officers, the nation’s highest office is determined by the Electoral College — an obscure vestige of the Constitution that was established as a compromise between empowering Congress or a popular majority with the ability to elect the president.

In every presidential election, dating back to the country’s first in 1789, voters cast their ballots for a slate of electors, who are often party loyalists nominated by a state’s political party to pledge support to the nominee.

The electors, who reflect the distribution of power across the states based on congressional representation, are decided every four years by each state’s political parties in the months before the presidential election. The process for choosing the electors varies by state, with some nominating their electors at party conventions, while others leave it to voters to elect them during the primary process.

The electors are often prominent figures in each party. In New York, both former President Bill Clinton and 2016 Democratic presidential nominee Hillary Clinton are electors for Biden, while Stacey Abrams, the 2018 Democratic gubernatorial candidate and voting rights advocate, will be an elector for the president-elect in Georgia. In South Dakota, where Trump won, Republican Gov. Kristi Noem, a possible 2024 presidential contender, will cast her vote for the current president.

When and where are the electors meeting?

The electors are required by federal law to meet the “Monday after the second Wednesday in December of presidential election years,” but they gather in each of their respective states and the nation’s capital at places determined by the state legislature.

“The Electoral College is not an institution. It doesn’t exist over time, it doesn’t even exist in any one physical place. It’s the series of electors coming together for this one moment and then dissolving,” said Richard Pildes, a professor of constitutional law at New York University and an expert on election law. “And once they have cast their vote, those votes can’t be changed.”

Most will convene inside the chambers of their state capitols to cast separate ballots for president and vice president. The time of the meeting is also set by each state, so expect votes to be cast throughout the day on Monday, starting at 10 a.m. ET.

In the middle of a pandemic, a number of states are transforming the quadrennial gathering from pomp and circumstance to a bare-bones formality with much smaller crowds and limited public access, if any.

What happens on Monday?

Each state’s slate of electors will cast two votes by a paper ballot in a typically low-drama affair.

Once the votes are tallied, the electors sign six certificates with the results. The separate certificates are submitted to the archivist of the United States, the president of the Senate (the country’s vice president), the secretary of state and to the judge of the U.S. district court of the district where the electors met.

The candidates who receive a majority of the vote across the Electoral College — or 270 votes — are formally elected to the White House.

What about so-called ‘faithless’ electors?

Some experts aren’t anticipating any spectacles with “faithless” electors this year.

“Because Joe Biden has won with such a large surplus of electors, the temptation for any one or two electors to defect is not present because it couldn’t possibly affect the outcome,” Pildes said. “[And] if the political parties have done their job in putting forward slates of electors who are going to honor the popular vote in the state for their candidate, which we have every reason to believe they were, then the electors are going to vote in accord with the popular vote in their state.”

But it is still a possibility.

Some can break their pledge to vote for their party’s nominee, as seven successfully did in 2016, but this has happened very few times in the nation’s history.

Earlier this year, the Supreme Court ruled on the “faithless electors” case, making it constitutionally permissible to bind electors to vote for the popular vote winner.

Thirty-three states, 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.

What happens next?

The meeting of the Electoral College marks the culmination of a long and an arduous election, one that took place in the midst of unprecedented circumstances. But the process for formalizing the election does not end with the vote by the electors.

The process then moves to Congress, where a joint session of the Senate and House meet on Jan. 6 to count the electoral votes.

Some theatrics are expected when Congress gathers. At least one Republican House member, Rep. Mo Brooks of Alabama, plans to object to the slate of presidential electors from multiple states — an effort that would likely only make a symbolic stand, and delay the certification of the presidential race results by hours, rather than alter the election results.

Under federal law, a member of the House or Senate can contest the Electoral College results from any state, forcing the House and Senate to separate for up to two hours of debate and vote on whether to accept a slate of electors. A majority of both chambers would have to support the motion to successfully challenge a given slate of electors, according to the Congressional Research Service.

Most states are shielded by the “safe harbor” provision, which is part of a federal law that says if states resolve election-related disputes, including recounts, audits and legal fights, before the deadline, their electoral votes are considered “conclusive” and binds Congress to count them. All but one state, Wisconsin, successfully settled challenges over the results of the election before this year’s date, which fell on Dec. 8.

While the battleground might not fall under safe harbor status, experts told ABC News it might not matter all that much, particularly without dueling slates of electors at play.

“Safe harbor makes it kind of beyond dispute, but the lack of safe harbor doesn’t all of the sudden open up some big question about who the electors from Wisconsin are,” said Kate Shaw, a Cardozo law professor and ABC News legal analyst, who called the statute not “terribly significant.”

“If you miss the safe harbor day, Congress isn’t obliged by the Electoral Count Act to count those electoral votes,” said James Gardner, a professor of law at the University of Buffalo who specializes in election law. “That doesn’t mean that they won’t. They will. … It’s mainly of a more theoretical than practical significance in most circumstances.”

ABC News’ Benjamin Siegel contributed to this report.

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