President Trump leads by nearly 700,000 votes in Pennsylvania as of 5 a.m. on Wednesday, and Mr. Biden’s chances depend on whether he can win a large percentage of the more than 1.4 million absentee ballots that remain to be counted.

So far, Mr. Biden has won absentee voters in Pennsylvania, 78 percent to 21 percent, according to the Secretary of State’s office. The results comport with the findings of pre-election surveys and an analysis of absentee ballot requests, which all indicated that Mr. Biden held an overwhelming lead among absentee voters.

If Mr. Biden won the more than 1.4 million absentee votes by such a large margin, he would net around 800,000 votes — enough to overcome his deficit statewide.