The million-dollar question on the election’s eve: Who is left to vote?

After weeks of record-breaking participation in early and mail voting in dozens of states, one critical question remains on the eve of the 2020 presidential election: Who is left to vote?

More than 98 million Americans had cast ballots by Monday evening, an astonishing figure equal to about 70 percent of the total turnout four years ago — leaving election officials, the campaigns and the public overall wondering how heavy voting traffic would be on Tuesday.

While at least three states — Texas, Hawaii and Montana — exceeded their total...