Unlike the more recent presidential elections, we enter Tuesday's vote with the very real potential we don't know the winner at the end of the night.
The COVID-19 pandemic has upended the voting process, leading to a surge in the number of people voting absentee or early.
This changes the dynamics for how results are delivered, so here's a look at what we can expect on the night:
Expect some races to be called early
While there have been reminders that results "could take days," that's not the case in all states. You can expect states that are traditionally Democratic/Republican strongholds to be called fairly early on if the early counts are trending the way you'd traditionally expect.
The Associated Press for example says it may declare a winner of a state immediately after the polls shut based on interviews it's conducted with voters during the day.
Closer races will take longer to determine
When a race is closer, the likes of the AP and the major TV stations that "call" results will take longer, and will monitor vote counts in key counties and compare it with party enrollments and trends in previous elections to see if there is any possibility that the losing candidate can catch up.
Expect them to be more cautious this time around due to the significant variation in how voting has been conducted this year, such as the huge increase in early voting and absentee ballots, as well as differing deadlines a state has for when mail-in votes can be received and counted.
Mail votes take longer to process than in-person votes, and states have different rules about when they can start processing and counting absentee ballots. Minnesota is able to process and count its absentee ballots from 14 days before the election, though the tallies aren't reported until the polls close on election night.
It was also initially thought that Minnesota's result wouldn't be known on the night, but with a court ruling meaning that any ballots that arrive after Nov. 3 must now be segregated pending a possible legal challenge, and with counting of absentee ballots starting 14 days in advance of Election Day, it's possible that Minnesota's race is called sooner, albeit the final tally still subject to further action.
By contrast, in Wisconsin, absentee ballots can't begin being processed or counted until 7 a.m. on Election Day, meaning its mail ballot results will likely be far later than Minnesota's. Pennsylvania absentee ballots can't be processed till 7 a.m. Election Day, and can't be counted till 8 p.m.
That said, if there's a sign that even in swing states one candidate appears to have the clear advantage based upon the votes that have already been counted, the ballots that have yet to be processed or received, and the demographics of the areas they're likely to be coming from, it could be that such a race will be called on the night.
Otherwise, it could be Wednesday, Thursday or even longer depending on how close it is, with NPR reporting the likes of Michigan and Pennsylvania may take a few days before results are tallied in full.
States like Arizona, for example, also accept ballots for several days after Election Day provided they're postmarked no later than Election Day itself. As a result, final tallies may not be achieved till the end of the week or even into the weekend.
Expect results from states like Florida, which allows absentee ballots to be processed early but doesn't accept ballots that arrive after Election Day, to be called on the night, though final tallies may take a day or two longer depending on how many absentee ballots arrived on Election Day or the day before.
In any case, be skeptical if someone "calls" a swing state super early after the polls close, it's likely to be several hours or potentially days before we know for sure.
So will we know results on Election Night?
It's still possible that the presidential race could be called on Election Night, but it depends on how close it is and how many votes are being reported.
FiveThirtyEight says there's a "good chance" we won't know the winner but we should have a "pretty good chance" of knowing which way the vote is going on the night even if no candidate has enough to claim 270 Electoral College votes yet.
It says of the swing states:
"We should get near-complete results in Florida in a matter of hours; Arizona and North Carolina will release the vast majority of their ballots very quickly, although if the race is too close to call they may not provide a final answer for days. Georgia and Texas should tally most ballots on Nov. 3, but counting may stretch into Wednesday or Thursday. We should know the winner in Wisconsin by Wednesday morning; Michigan and Pennsylvania, by contrast, will probably take until the end of the week."
For down-ballot races, expect a similar situation where easy victories are called early, while closer races may take longer. With state-level races, there's also variation depending on the efficiency of vote counters, the number of votes cast, and the speed at which results can be reported.
Reminder: It's never been the case that all votes are counted on Election Day
Despite President Trump's desire that only votes counted on Election Day should be permitted, suggesting this week that those states that wish to count after Nov. 3 will be blocked by the courts, it's never been the case that all votes have been counted on Election Day.
As the New York Times reported this week, it's not physically possible for the 50 states to count every single vote cast by midnight, and it's never been expected of them.
The date by which votes have to be certified varies by state. It's as little as two days in Delaware and more than a month later in California. Minnesota's results will be certified on Nov. 24.
Any attempt to block ballots from being counted after midnight would disenfranchise millions of voters – even in 2016, the race wasn't called for Donald Trump until shortly before 3 a.m. based on the results coming in from Wisconsin.
In the past, the only reason we have an idea of who won is because news outlets project the winners based on incomplete counts, when they're confident that it would be unrealistic for their opponent to claw it back. In any case, it's not confirmed till all votes have been tallied and the results certified.
Very occasionally news outlets will get it wrong, most famously when the AP called for Al Gore in Florida in 2000, but the news organization notes that in 2016 its vote calls were 99.8% correct, and 100% correct in all presidential and congressional votes.