When will we find out who the president will be? What to know for ...

When will we know who will be the next president of the United States? The answer might not be known on Election Day, many experts say.

While there remains uncertainty in just how long the results could take before a winner is called, both legal and political experts say an answer could take days.

The answer hinges largely on one detail.

"The final results are going to be months, because they have to be audited and they have to be canvassed and they have to be signed off on. But when will the American public know who they can confidently think is going to be our next president? That all depends on the margin, right?" Noah Praetz, president of The Elections Group and previous director of elections for Cook County, told NBC Chicago. "But I'll tell you this, my sense is that most of the swing states are going to be able to have counted preliminarily at least all of their ballots, certainly by midday Wednesday. Arizona is a bit of a outlier, but they rely a lot more on mail balloting and those things just take a little bit longer than doing volume. So I think Wednesday would be a good time to have a sense of things."

Experts say the gap between the candidates will play a major factor in when results are called and what happens in the day after the election.

"I think the problem really in 2020 in the litigation was that they couldn't show that even if they could prove their allegations that it would change the election result ... They didn't affect enough votes to change the election result and that has to do with the size of the margin of victory for [President Joe Biden] in 2020," said Professor Michael Kang of the Northwestern University School of Law. "So I think looking forward to this election one really important variable is the margin of difference between the candidates. If we have a reasonable size margin between the candidates it's really hard for the losing candidate to challenge that result."

Still, Kang said what happens on election night could play a role in the days that follow.

"This is going to take a few days, but if Trump declares himself the winner on election night it puts a ton of pressure on the process. You have this initial count that will come out and probably by the end of the week we'll have a determination of who seems to be the winner by the initial tabulation. If the outcome is very close in certain states it will trigger a recount," Kang said. "Sometimes that's automatic under state law. Sometimes the losing candidate has to issue for a recount. Sometimes that's pay the cost, which if it's going to change the outcome either candidate would be happy to do, and then you have the recount certify who is the winner after that. Beyond that you have another potential process which is the contest phase of election. So under state law, the losing candidate sometimes will bring an allegation that there's fraud, wrongdoing, mistake, some sort of irregularity that puts the outcome even after a recount into question."

While it is not unusual for results to take time in a presidential race, 2024 will see some changes that could delay answers for voters.

"This is going to be Election Week, not Election Day," said Democratic strategist Peter Giangreco.

Changes to voter ID laws and the early voting process in North Carolina could slow vote counts.

Meanwhile, laws in key swing states like Wisconsin and Pennsylvania mean clerks are unable to process mail-in ballots prior to Election Day. In 2020, those states were decided by approximately 20,000 and 80,000 votes, respectively.

“In other states, they can open them up, they can verify them. They can flatten them out, so all they have to do is run them through the scanners. In Pennsylvania, they can't even touch them," Giangreco said. "So, we're probably looking at Friday or Saturday before we know Pennsylvania.”

Delays aren't unheard of in a presidential race however, according to Dr. Kevin Boyle, chair of the history department for Northwestern University.

“There are a lot of stories of presidential candidates just going to bed not knowing whether they had won the presidency or not," Boyle said.

In 2020, it took four days before President Joe Biden was officially called the winner. In 2000, results hinged on just 537 votes in Florida, with networks calling the state for Al Gore, then George Bush before ruling the race "too close to call."

There are many elections throughout the 19th and 20th centuries that weren't called on election night.

“Even as late as 1960, John Kennedy wasn't announced as the winner of the presidency until the next day," Boyle said. "Richard Nixon wasn't announced as the winner of the presidency in 1968 until the next day. And then what happened was kind of the explosion of exit polls, which made it easier to pick a winner faster, to name a winner faster. And a lot of elections weren't very close until 2000.”

Still, Kang said elections have only grown more secure over the years.

"I do want people to not freak out about the election because actually we've gotten better at running these elections than we did in 2000," he said. "There's no comparison to how efficiently elections are run today and how professionally they're run today as compared to 25 years ago."

That doesn't mean elections now are completely free of error, however.

"Running a secure election doesn't mean it's perfect or free of error. It means it's resilient. So there's a backup plan for everything. Now, the most common things are a poll worker oversleeps or the person who's going to unlock the polling place didn't get there in time so it opens a little bit late. Those things are going to happen everywhere all over the country," Praetz said. "They're going to be highly localized, you know, disruptive, but correctable issues, right?"

Beyond delays in vote counts, experts also say legal challenges are likely before a final announcement is made.

Sharon McMahon, a podcast host and former educator known as “America’s Government Teacher," said there are a "very, very large myriad of lawsuits that are already in process and are going to be filed."

"There are already over 100 lawsuits in the works related to the election, and there is absolutely more that are on the desks of lawyers. They're just waiting to plug in the right details and waiting to file those," McMahon said. "If we think there were 60-plus lawsuits in the post-2020 election, there's probably going to be double that in this election.”

So what would it take to find out results sooner?

Giangreco said there's one scenario where results could come in closer to Election Day.

“Only if [Donald] Trump wins Wisconsin or Michigan," Giangreco said. "If he wins either those states, it's probably over with. And if we know those states on Wednesday, that'll probably be it. I think the most likely path for Kamala Harris to the presidency is the blue wall states: Wisconsin, Michigan, Pennsylvania.”

Whether that will happen is unclear.

“This is what it comes down to: If the polls are right and things are even, there's a massive advantage for Harris on the ground, especially in the blue wall states, and I think that's her ticket to win. If there's the response bias that we did see in 2016 and we did see 2020, where the polls undercount Trump voters, then you could be looking that Trump's really up four or five points in all these states, and it'll be an electoral landslide for Trump, and maybe even a popular vote win. So either the polls are right and Harris's field operation is going to win it or the polls are wrong, and it's going to be a good night for Trump.”

One other potential scenario looms this fall: the "contingent election" of the president and the vice president that would happen if no one can secure the 270 electoral votes needed to win the presidential election. 

That has not happened in the modern era, but there are a few conceivable (if unlikely) paths across the Electoral College map that could lead to Trump and Harris ending the race tied at 269 electoral votes.

In the event of a tie, Congress would decide the next president.

To track live Illinois election results Tuesday -- and beyond -- from around the state, bookmark this page on NBCChicago.com and the NBC Chicago app.