On almost everyone's mind this week: Who will win the 2024 presidential election and when will we know?

There is no clear answer to either question, but history—and inside information shared with the Daily Beast about Kamala Harris' campaign—suggests that we may not have a declared winner for days or possibly weeks after polls close Tuesday night.

States will release unofficial results Tuesday evening, which news networks and the Associated Press will use to predict winners and determine the race in most states. However, election officials in the seven swing states – Pennsylvania, Michigan, Wisconsin, North Carolina, Georgia, Nevada and Arizona – are already asking voters to be patient as vote counting will not be completed on Election Day.

Could 2020 repeat itself?

Four years ago, the AP declared that Joe Biden defeated Donald Trump on Saturday, November 7, four days after polls closed across the country. The days-long delay in announcing a winner was largely due to Pennsylvania, Arizona and Nevada.

This trio of states will likely hold the nation on tenterhooks again, according to a chart compiled by the Harris campaign and provided to the Daily Beast. Virginia, Ohio, Colorado and Florida are said to have near-complete election results by 10 p.m. EST on election night, which could be a good barometer of where things stand for either candidate – based on margin of victory – even if those states do this It is not expected to be flipped.

Harris' team's spreadsheet then assumes that “most results” from Georgia, North Carolina and Michigan will be available before midnight on Election Day, and that Wisconsin will be added to that list at 6 a.m. EST Wednesday morning. During the same period, the campaign estimates that only “partial results” will still be released in Pennsylvania, Arizona and Nevada.

The campaign notes that “tens of thousands” of provisional ballots in Pennsylvania, overwhelmingly considered a key swing state for both Trump and Harris, cannot be legally counted until Friday.

It's not just Harris' campaign warning of a long wait. Derek Tisler, an election administration and security expert at the Brennan Center for Justice, told NPR this week that voters can at least expect “a similar timeline” to 2020.

Tisler also noted that the election winner may not be known for “weeks” as polls suggest a closer race than four years ago. He suggested this could happen if the results are within a few thousand votes in a tipping point state.

What factors could hinder the vote count?

Why the long wait? The main driver in 2020 was legal restrictions on when officials in key states can begin processing mail-in ballots. Tisler shared that, aside from Michigan, there have been no major changes that would indicate that there will be drastic changes in the speed at which voting will be tabulated this time.

“So when we talk about processing ballots, we're talking about absentee ballots,” he told NPR. “And counting absentee ballots takes longer because poll workers have to go through all of these steps before they can actually count those ballots.”

These controls include the need to confirm a voter's identity and eligibility, as is the case at an in-person polling place. Anyone who counts mail-in ballots must also check the ballot for damage before it can be placed in a scanner and counted.

Michigan proactively changed its state law, allowing it, like most states, to process mail-in ballots before Election Day. However, this is still not the case in Pennsylvania and Nevada and delays are to be expected.

Arizona state law allows absentee ballots to be processed before Election Day, but there are particularly long ballots in this election that are expected to slow things down. The Washington Post reports that ballots in Maricopa County, the state's most populous, are two pages long this year, requiring ballots to be folded out and twice as many pages fed into voting machines, which is more laborious and leads to an increase of could cause paper jams.

In Nevada, mail-in ballots without a postmark that arrive by Friday are counted, and those with a postmark are allowed to arrive by Saturday and still count. That's radically different from most states, which require mail-in ballots to arrive by Election Day, and could cause significant delays if the election is as close as polls suggest.

Dangers of a lengthy election count

Tisler said this waiting game could become dangerous if one side – be it voters, partisan media, the candidates or their surrogates – tries to fill this “information vacuum by spreading false claims” or prematurely declaring victory.

“Everyone is really eager to learn more about something they are very passionate about,” he said. “But the problem is that until those votes are actually counted, there's really no new information to provide to these people… I encourage everyone to be patient. And again, understand that the reason we are waiting for results is because the electoral process puts accuracy and security first.