After weeks of campaign ads, political speeches and voting in more than two dozen primary contests, Americans are coming to terms with a reality that many have tried to avoid: a rematch.

For months, large swaths of Democratic, independent and moderate Republican voters have moved through familiar emotional stages, processing the prospect of President Biden and former President Donald J. Trump fighting it out, once again, for months. They have dealt with denial, believing other candidates would emerge, and bargaining, entertaining fantasies about last-minute entrants, nationally viable third-party candidates and speedy legal prosecutions. They have fought depression, as options failed to materialize.

And now, slowly but surely, acceptance has begun to arrive.

“You ever hear people say, ‘You’re picking, but that’s not the choice you want’?” said Shalonda Horton, 50, as she walked into a polling place in Austin, Texas, to vote for Mr. Biden on Tuesday. “When I get in there, I’ll say, ‘Lord, help me.’”

In Los Angeles, Jason Kohler, who calls himself a progressive Democrat, said he was casting his ballot for Mr. Biden only with resignation. But he has made his peace.

“Lesser of two evils at this point, you know?” said Mr. Kohler, 47. “Voting is enough of a duty for a citizen, so I feel like you got to do it.”

Complaints about politicians are as old as American politics itself. But pollsters and strategists believe something different is happening this year. Rarely have so many Americans been so unhappy with the direction of the country for so long. Rarely have so many voters said for so long that they want different leaders. The voters who dislike both Mr. Biden and Mr. Trump are talked about so often that they now have their own political moniker: double haters.