Mail ballot processing involves everything from opening envelopes to checking voter signatures to flattening ballots that have been crumpled or creased in transit. The procedures can be time consuming, and that will create a backlog of millions of votes set to draw out the counting process for days after the polls close.

That means that the country may be waiting, along with voters in the three Midwestern states, to see whether Trump or Joe Biden carried their electoral votes — and potentially the presidency.

“People kind of underestimate the enormity of that task,” said Ohio Secretary of State Frank LaRose, a Republican, as he ticked through the long processing checklist that each ballot must go through before it can be counted. LaRose’s state, unlike many of its neighbors, lets election authorities start processing ballots earlier. “God forbid we had to do all of that on election night.”

A handful of states including Ohio and Florida, another key battleground, allow election officials to process or even count mail ballots early, meaning they typically report results quickly even when there is heavy mail voting.