“I think we have an electorate that’s going through the stages of grief about this election,” said Sarah Longwell, who conducts regular focus groups with voters across the political spectrum as co-founder of Republican Voters Against Trump. “They’ve done denial — ‘Not these two, can’t possibly be these two.’ And I think they’re in depression now. I’m waiting for people to hit acceptance.”
...
North Carolina Gov. Roy Cooper, a Democrat, said many voters are recovering from what he called “a knock-down, drag-out fight” that was the 2020 presidential election.

“Many of them have not wrapped their heads around the fact that it is, in fact, going to be a rematch,” Cooper said in an interview. “When they do, I don’t think there’s any question that Joe Biden is going to win the day.”

I hadn't thought specifically about this, voter fatigue, an enthusiasm gap, the stages of grief. I think that that's accurate. "Haven't wrapped their heads around" it: yeah, I think that's true, too. The commentariat, including in this article from AP, are noting "Only 6 Months Until the Election!". Man, historically, voters didn't start paying attention until after Labor Day. That has certainly changed, and not just in the last two cycles, but six months is a long time for people. They've got real lives: jobs, families, friends, birthdays, holidays, summer vacations. Democracy makes demands on voters; Americans (mostly) believe in it, they do their duty, especially in presidential election years, but America is not Israel, not Weimar Germany--you can't impose on everyday people the duty to remain at Defcon 5 readiness in politics every day for months or years. They're not going to be scurrying from work to the polls every six months or a year. That's not a normal country. 

I agree with Gov. Cooper that when voters focus, however reluctantly, that we will choose, there really is no choice, President Biden. Given voter fatigue and an enthusiasm gap, the "ground games" of the campaigns will be the key. GOTV, Get Out The Vote, is the sine qua non of every campaign, it was on every campaign I ever worked on going back to the 1970's. It's easier now with mail voting than it was then, but the gameplan is the same. Identify your voters in polling in the summer and get them to the polls (or make sure they mail in their ballots) when voting begins. And in this, the president's reelection team has an insurmountable, yes, I am using that word, advantage. Electoral politics is still a retail operation with a one day sale. President Biden will close the sale.