If the election results Tuesday come down to a razor thin margin, the fate of the presidential race could very well hinge on the consciences of four, unelected citizens whose names you’ve never heard: Robert Satiacum, Bret Chiafalo, Baoky Vu and Chris Suprun.

Two are Republican. Two are Democratic. And all four are threatening to become what’s known as “faithless electors”—citizens sent to the Electoral College who break their pledge to vote for their party’s ticket.

Satiacum, a Democratic elector from Washington who supported Vermont Sen. Bernie Sanders in the primary, swears up and down he won’t vote for Democrat Hillary Clinton. “No, no, no on Hillary. Absolutely not. No way,” he told the Seattle Times last week. Chiafalo, who is also a Democratic elector from Washington, is in the same boat. Having originally supported Sanders, he says he doesn’t know if he can in good conscience cast an electoral vote for the Democratic nominee.

Meantime, Vu, an immigrant and Republican elector from Georgia, says he can’t reconcile his position on immigration with a vote for Donald Trump, while Suprun, a Republican elector from Texas, so dislikes the GOP nominee that he told Politico he’d consider casting a vote for Clinton instead. (Suprun told TIME Tuesday that he intends to support Trump.)

If any of them act on their promises, it would be rare. In the 240 year history of the U.S., there have been 157 faithless electors, according to the nonprofit FairVote. Nearly half changed their votes because the candidate to whom they were pledged died before the Electoral College met, three chose to abstain and the other 82 broke their pledge for reasons of personal preference or conscience. But none has ever successfully changed the outcome of an election.

This year could be different. If the margin of victory for either Trump or Clinton in the 538-seat Electoral College comes down to one or two votes, as it did in 2000, it’s possible that a faithless elector could keep a candidate from passing the halfway mark, banking 270. While that exact scenario has never happened, it’s been close. In the 2000 election, for example, George W. Bush won the Electoral College by just five votes—271 to 266, with an elector from Washington, D.C., choosing to abstain. If just three electors had flipped their vote in that case, Gore could possibly have become president.

There’s a big if there, however. If an election comes down to a skirmish in the Electoral College, what actually happens will likely depend on a patchwork of state laws and constitutional checks.

In Washington state, for example, it’s technically illegal for an elector to break his pledge to his party, although the ramifications are minimal and no elector has ever been prosecuted. If Satiacum and Chiafalo follow through on their threats to break their party pledge, they could be slapped with fines of around $1,000. In Georgia and Texas, where there are no laws governing electors, Vu and Suprun would face no consequences.

But that doesn’t mean their votes will necessarily stand. If any faithless elector ends up swaying the outcome of the election, federal lawmakers have a couple of avenues of recourse, both of which are baked into the U.S. Constitution.

The first applies if an elector abstains or flips his vote in such a way that it results in an Electoral College tie. In such a case, then a little known provision buried in the Twelfth Amendment mandates that the House decides the president, while the Senate chooses the vice president. Each state delegation in the House casts one vote for president, and whichever candidates get the simple majority wins.

The second constitutional check is more broad. On January 6, 2017, the newly elected Congress will meet to determine if the Electoral College vote was “regularly given.” For most of the country’s 57 past presidential elections, this vote has been ceremonial. But it doesn’t have to be. If just one House member and one senator objects to the way that the Electoral College vote played out—for example, if a faithless elector swings the final tally—then the new members can retreat to chambers to vote on what to do about it. If the House and Senate agree, their decision is final. If the House or the Senate do not agree, then the dispute goes to the “executive of the state,” meaning the state’s Secretary of State, who would make the final call.

In other words, if Satiacum, Chiafalo, Vu, or Suprun cast a vote that ultimately alters the course of the election, and anyone in the newly-elected House or Senate balks, then the decision, in all likelihood, will be delegated to Washington Secretary of State Kim Wyman, Georgia Secretary of State Brian Kemp, or Texas Secretary of State Carlos Cascos. And while it’s impossible to say what, exactly, those state chiefs would choose, they would be under extraordinary pressure to honor the voters’ will.

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Write to Haley Sweetland Edwards at haley.edwards@time.com.