When will we know the U.S. election winner? Maybe a minute past midnight

Many millions of eyes around the world could find themselves glued to data emerging from Pennsylvania sometime around midnight eastern time on U.S. election night.

It comes down to the math of presidential elections — and how the pandemic has permanently altered it by popularizing mail-in voting, especially among Democrats.

Nowadays, predicting the winner requires factoring in results from both mail-in and in-person ballots, along with how many of each remain uncounted.

It so happens that Pennsylvania, the state that's probably most critical to crowning the winner, has a law requiring the vast majority of its counties to publish some mail-ballot statistics by 12:01 a.m. ET on Wednesday, Nov. 6.

News organizations' number crunchers will then plug those stats into spreadsheets and calculate the likelihood of either candidate emerging victorious in that vital state.

By that point, we should already have a sense of who the frontrunner is, courtesy of two southeastern swing states: Georgia and North Carolina. 

The polls close in Georgia at 7 p.m. ET and in North Carolina at 7:30 p.m. ET, and both states have laws that should enable timely processing of mail ballots. 

A top election-data analyst expects to have a good idea who's won those southern states sometime between 10 p.m. and 11:30 p.m., unless it's too close to call. 

"That's going to be our first set of clues to how this may go," said Drew McCoy, president of the election-reporting service Decision Desk HQ.

In summary: If either candidate wins both southern swing states, they immediately become the commanding favourite. In the case of Donald Trump, he would be on the cusp of victory. If he subsequently wins Pennsylvania, it's lights out: the 45th president is a near-lock to become the 47th president.

"It's over," if Trump wins North Carolina, Georgia and Pennsylvania, McCoy said. He would hit the magic number of 270 electoral votes, barring a shock event like Harris winning, say, Texas or Florida.

In other words, Pennsylvania becomes the kingmaker. Which brings us to that midnight data dump.

Under a law passed in 2022, Act 88, the state's 67 counties were offered grant money for new election equipment and staff, but there are strings attached: To get the cash, they have to publish data on the number of outstanding mail ballots.

The mail ballots take longer to process. It requires opening envelopes, checking signatures, confirming the identity of voters, placing ballots in piles, then sliding them into machines.