Democratic nominee Kamala Harris (L) and Republican nominee Donald Trump.

With Democratic nominee Kamala Harris and Republican nominee Donald Trump heading into election day in a near-dead heat, early predictions about victory for either side, as well as when the election will be called, feel ill-advised as of Tuesday afternoon.

In 2020, the last US Presidential election, Democratic nominee Joe Biden wasn't declared the winner until four days after polling day when several American news agencies called the state of Pennsylvania in his favor. 

In-person polling stations opened in the US at varying times across the country on Tuesday morning, though many voters have already taken advantage of mail-in voting and early voting where available.

The University of Florida's Election Lab reported on Tuesday afternoon that more than 85 million early votes - 46 million in-person votes and 39 million returned mail-in votes - had already been cast for the 2024 US Presidential election.

However, states have varying rules about when they can begin both processing and counting their mail-in and early votes which could impact when results become available.

While tens of millions of people have already cast their vote for the 2024 US Presidential election, many more are expected to vote in person on Tuesday. 

Polling locations, which are dictated by a voter's primary residence, are generally open for about 12 hours on election day, which is not a federal holiday in the US.

Voters must be registered to cast their ballot on election day, except for in North Dakota, where a valid ID suffices. 23 states allow for same-day registration, while others, including New York, have a deadline prior to election day.

According to the Associated Press, polls in Georgia, Indiana, Kentucky, South Carolina, Vermont, and Virginia will be the first to close on Tuesday at 7 pm ET. Exit polls could start to emerge around that time, though many are advising not to place too much stock in them considering how close the race is.

Polls in California, Idaho, Oregon, and Washington will close at 12 am ET, with the country's final polls closing in Alaska and Hawaii at 1 am ET.

However, if voters are still in line at closing time, they are legally permitted to still vote, even if the closing time has passed. As the saying goes, "If you're in line, stay in line."

The US elects its president through the electoral college, not by popular vote. Indeed, a candidate could win more votes than their opponent and still lose the electoral college and thus the presidency. The Bipartisan Policy Center notes that an election in which the winning candidate for president did not win the most individual votes has only occurred five times in US history, most recently in 2016.

The first candidate to win 270 of the 538 electoral college votes will win the US presidential election. 

So, when will we start seeing results?

After acknowledging that "this race continues to be extremely close," Jen O'Malley Dillon, the Campaign Chair for Harris for President, provided this timeline of what her team is roughly expecting to see:

Tuesday, 7pm - 10pm EST

  • Most results from Georgia and North Carolina, but if these races are close, they may not be called
  • Partial results from Pennsylvania, Wisconsin, and Michigan
  • Near-complete results from Virginia, Florida, Ohio, and Colorado

Tuesday, 10pm - 12am ET

  • Most results from Georgia, North Carolina, and potentially Michigan, but if these races are close, they may not be called
  • Partial results from Pennsylvania, Wisconsin, and Arizona
  • Initial results from Nevada

Wednesday, 12am - 6 am ET

  • Additional results from all states, particularly Pennsylvania, Arizona, Nevada, Michigan, and Wisconsin
  • If results are very close in any state, the race still may not be called

Thursday and beyond

  • Results may continue to trickle in from all states, particularly Pennsylvania, Nevada, and Arizona
  • In Nevada, ballots can continue to arrive through November 9, and voters can cure ballots through November 12
  • Late counting: In Pennsylvania, we expect tens of thousands of provisional ballots that will be counted starting November 8; in North Carolina, there may be challenged ballots that are not counted until November 15
  • If results are very close in any state, the race still may not be called.

O'Malley Dillon said: "It will take a long time to count every single vote, and we can't place too much stock in the early returns.

"The tally in certain states is going to change a lot as additional ballots are counted. For example, some states that count absentee ballots first may start off blue [Democratic] and shift to red [Republican] as time goes on. These would be your Michigans and Pennsylvanias.

"On the other hand, there are states like North Carolina, Arizona, and Nevada where we may see Republicans leading from the beginning and then those states may shift to blue as urban areas come in and more late early vote and vote-by-mail is counted."

She added: "We may not know the results of this election for several days. But we must stay calm and confident during that period of time.

"We all have a role to play to ensure that our friends, family, and neighbors trust our electoral process."