Americans have two big questions ahead of another election with a deeply divided electorate: Who will win and when will they know?

In 2020, election week replaced election night: Joe Biden was only declared the winner on Saturday. This year it could go either way. It could take up to a week for the NBC News Decision Desk to predict a presidential winner, or it could happen as early as Wednesday, even Wednesday morning.

The truth is that the Decision Desk can't know what scenario will unfold until election night, no matter how carefully we have analyzed the polls, early voting and other election-related data. The answer depends not only on how states count their votes, but also on the unforeseeable factor of how close the margins will be.

One thing is clear: the days of predicting a winner on election night are almost certainly over.

In order to predict a presidential winner as early as Wednesday, the key battleground states, particularly Pennsylvania, would not necessarily have to be tied. The gap between first and second place would have to be large enough to predict a winner.

Races that are nearly undecided, like the 2020 presidential elections in Georgia and Arizona (Joe Biden's margin of victory in those states was 11,779 and 10,457 votes, respectively), essentially require all votes to be counted before NBC News' Decision Desk can project one Winner. This can take days.

But let's look at the battleground states where calls are at least possible on Wednesday.

How the critical “blue wall” states count their votes – and how that differs from 2020

Any path to capturing the White House will likely lead through the “blue walls” of the states of Pennsylvania, Michigan and Wisconsin. In 2020, Pennsylvania was the key electoral state that decided the presidency, and there's a good chance it will take on that role again. But in 2020, it took four days after Election Day for the NBC News Decision Desk to declare a winner.

It could well happen much earlier this year. That's because 98% to 99% of Pennsylvania's votes are expected to be counted by Wednesday morning.

The way Pennsylvania counts its votes remains largely unchanged since 2020, but the process is expected to be more efficient this year. Major counties like Allegheny (home to Pittsburgh) and Philadelphia have invested heavily in new voting machines and hired more staff to help process ballots. Also remember that this election is not being conducted in the midst of a global pandemic, which required strict social distancing between election officials, slowing the count.

We expect several Pennsylvania counties to release large numbers of early voting shortly after polls close, followed by in-person voting on Election Day. That would mean that the early votes received on Election Day and the provisional ballots would still have to be counted on Wednesday.

If 99% of the total votes are counted quickly, a forecast for Wednesday in Pennsylvania is quite possible unless the race is extremely close. In 2022, we had about 90% of votes counted in Pennsylvania when, at 12:51 a.m. ET, the NBC News Decision Desk projected Democrat John Fetterman as the winner of the state's Senate race.

In Wisconsin and Michigan, the majority of votes could also be counted by Wednesday if previous reporting patterns hold.

Based on these patterns, the amount counted in Wisconsin should be over 99% by Wednesday morning. In Michigan it is likely more than 95%. One important note in Michigan: For the first time, communities with more than 5,000 residents can begin pre-processing mail-in ballots — opening envelopes, verifying voter signatures, etc. — several days before the election, which could lead to a more efficient ballot count that night.

On the other hand, the introduction of early in-person voting in Michigan could make it more difficult to count votes quickly. Despite these changes, both Michigan and Wisconsin count almost all of their votes quickly. So unless the races are extremely close, there's a good chance the NBC News Decision Desk will be able to make a prediction sometime on Wednesday.

However, when the races are so close together, it could take days or maybe even a week depending on the margin.

How the battlefields of the Sunbelt count their votes

Outside the blue wall, the critical swing states of Georgia and North Carolina are among the best in the country at efficiently processing and counting their votes.

These two states are also very good at making their data available to the public electronically. In Georgia, over 99% of votes are counted on election night. In fact, in the last election, almost all votes were counted by 1 a.m. ET. However, Georgia was so close in 2020 that it took days for the race to be decided.

North Carolina has a similar pattern of voting reporting: In previous elections, 99% of votes were counted by midnight. Still, any chance of predicting election night in any of these closely divided states depends on the margin between the two candidates being wide enough.

The one electoral vote awarded to the winner of Nebraska's 2nd Congressional District could also be crucial in the path to 270. Since there are no significant changes to how votes are counted in Nebraska, it is expected that around 90% of the votes will be counted by Wednesday morning, which in turn could lead to a forecast if there is enough distance between the candidates.

The final two battleground states, Arizona and Nevada, almost certainly won't be called anytime soon. If the presidency is left to one of these states, forget any thoughts of a Wednesday resolution.

In 2020, NBC News did not predict a winner in Arizona until November 12, nine days after Election Day. And unlike some other nearby states, it wasn't just because the margin was so narrow.

Typically in Arizona, up to 20% of votes remain to be counted after election night – mostly late-arriving mail-in ballots. And there are very significant differences between Republicans and Democrats when it comes to who votes and when (at the start or on Election Day). This makes it nearly impossible to predict a winner on election night in Arizona.

Nevada is a state that has a large number of early votes, both absentee and in-person, that will not be counted on election night. In the past, almost a quarter of the votes had still not been counted by the Wednesday morning after Election Day.

Given that the state has historically been close in presidential elections, the likelihood of a close race with many uncounted votes is very low.

Bottom line: In Arizona and Nevada, it will likely be a few days, maybe even longer, before the winner is announced.