The 2024 election looks extremely close in the polls. And if the actual results are that close after Election Day, it's possible the results in a key state could hinge on a recount.
The rules about when recounts happen and the procedures they include vary from state to state, since elections are administered locally. Those rules were in the spotlight in 2020, after Joe Biden won a handful of key battleground states by a razor-thin margin.
Former President Donald Trump requested, and was granted, recounts in a few of these states, but none of them changed the outcome of the election there. Typically, recounts only slightly change the final margin of a race, but when the vote is close enough, they can have a real effect.
Ahead of Election Day, here's a refresher of the recount rules in the states expected to be the closest in the presidential race.
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Arizona
Candidates don't request recounts in Arizona, but the state requires an automatic recount if a race is decided by a margin within (or equal to) less than 0.5% of votes cast in a race. The threshold was lower in 2020 (0.1%), but since then, the state enacted a law raising the automatic recount threshold to 0.5%.
A bipartisan group of lawmakers approved new measures in 2024 that would shorten the time needed for a potential recount. That means Arizona would be able to handle a recount and not miss the deadline for the December meeting where members of the Electoral College cast their votes.
Georgia
In Georgia, a candidate can request a recount if the margin of a race is within 0.5 percentage points, as long as the request is made within two business days of certification.
Georgia's 2020 presidential vote got significant scrutiny in the days after Election Day, given both the tight margin and Trump's baseless claims of widespread fraud.
Election officials hand-counted nearly 5 million ballots again after the election, as part of a statewide risk-limiting audit authorized by a new state law.
Then, after the state certified Biden's victory, the Trump campaign requested a machine recount, as was its right under state law. (That recount also didn't change the outcome.)
State law also allows election officials to ask for a recount if there is "a suspected error or discrepancy in the returns," and the secretary of state can ask for one if a candidate believes a "suspected error or discrepancy" occurred.
Michigan
Michigan law provides for an automatic recount if the margin of victory in a race is 2,000 votes or fewer. A candidate is also allowed to request a recount if they have a "good-faith belief that but for fraud or mistake, the candidate would have had a reasonable chance of winning," according to state law.
The state recently enacted changes to Michigan's recount law, but none will go into effect before Election Day.
Nevada
There's no provision for automatic recounts here, but a candidate can request one, as long as they cover the cost of the recount and make the request within three days of the certification.
North Carolina
A candidate can request a recount in a race if the margin of victory is within 0.5% of votes cast, or 10,000 votes, whichever is less.
Pennsylvania
The state automatically triggers a recount if the margin between two candidates is within 0.5%. But three voters can also request a recount in a specific precinct if they allege there was fraud or an error in that precinct.
Wisconsin
The state allows candidates to request a recount, as Trump did in 2020. But the candidate who requests the recount has to cover the expenses if the margin of victory is larger than 0.25 percentage points, as Trump did when he paid $3 million for a partial recount that resulted in no substantive change to the 2020 vote count.
This story first appeared on NBCNews.com. More from NBC News: