CHICAGO (NewsNation Now) — NewsNation’s television broadcast and digital properties will rely on The Associated Press for all vote counting and race calls. NewsNation chose to rely on the AP because they call races based on the facts.

“AP does not make projections or name apparent or likely winners,” said David Scott, a deputy managing editor who helps oversee AP’s coverage of elections. “If AP cannot definitively say a candidate has won, we don’t speculate.”

According to the AP, a race is only called when they “conclude that the trailing candidate will not catch the leader.” In fact, AP did not call the closely contested race in 2000 between George W. Bush and Al Gore, standing by its assessment that the margin in Florida made it too close to call. You can read more information about how AP calls races here.

We may not know who won the presidential election on Tuesday night. The biggest factor that may slow things down this year is the millions of Americans who voted by mail rather than risk being in a crowd during the coronavirus pandemic. In general, mail ballots take longer to count.

Election workers must remove the ballots from their envelopes, check for errors, sort them and flatten them — all before they can be run through scanners the moment polls close and be tabulated. In states with well-established vote-by-mail programs, this processing happens weeks before Election Day. The results are often released quickly.

But several states did not have this system in place before this year and laws on the books prohibited election officials from processing the ballots well in advance of Election Day. Without a head start, there’s virtually no way to process and count all the mail votes on Election Day, while also counting all the in-person votes.

There are three important battlegrounds with restrictions on when the mail vote can be processed — Michigan, Pennsylvania and Wisconsin.

In those states, Republican-controlled legislatures have resisted pleas from election officials to update the laws to allow for a speedier count. (The Michigan legislature did allow processing to begin 24 hours before Election Day in cities, but election officials say that’s not enough of a head start.) Instead, they will initially report in-person votes — expected to heavily favor Trump — and gradually update with the more Democratic-leaning mail ballots later.

“If Biden gets lucky and this is the Democrats night, by 11 or 12 o’clock on Tuesday we will know who is the next president. If things go as they usually do, we will have to wait for some slow counting states to present their votes,” Dr. Charles Zelden, a political science expert with Nova Southeastern University, said.

Not all battleground states are slow-counting states. So if several key states release their results promptly, one candidate may have a majority of the electoral vote — even without knowing who won in Wisconsin, Pennsylvania or Michigan.

It’s a scenario that puts a lot of eyes on Florida. The state allows its election offices to process mail ballots 22 days before the election. It’s also the biggest swing state. As long as the race isn’t too close — a big “if” in a place famous for tight races — there could be a close-to-complete count by midnight.

Two other Southern battlegrounds — North Carolina and Georgia — also can begin processing mail ballots early. They are both considered critical states for Trump. However, unlike Florida, neither state has a record of handling a large number of mail ballots. It’s unclear how quickly they will count those votes.

Finally, two Midwestern states — Iowa and Ohio — also allow for early processing of mail ballots. Trump won both states handily in 2016, but Democrats believe Biden is competitive there. Results in those two states on election night could give hints about what lies ahead in the critical Rust Belt states that take longer to count.

The Associated Press contributed to this report