Despite the fact the primary season has barely gotten underway, there simply is no alternative to Biden for Democrats who place winning in November over everything else.

These are Democrats who have been hit upside the head by reality. They know Biden is too old. But they also know that unless the president can be convinced to step aside for the good of the party and the good of the country, Democrats are stuck with him.

Ezra Klien, one of the sharpest analysts on the left, believes that it's not a matter of whether Biden would be capable as president. The question is whether Biden is capable of running for president.

New York Times:

We had to wait till this year — till now, really — to see Biden even begin to show what he'd be like on the campaign trail. And what I think we're seeing is that he is not up for this. He is not the campaigner he was, even five years ago. That's not insider reporting on my part. Go watch a speech he gave in Pennsylvania, kicking off his campaign in 2019. And then go watch the speech he gave last month, in Valley Forge, kicking off his election campaign. No comparison here. Both speeches are on YouTube, and you can see it. The way he moves, the energy in his voice. The Democrats denying decline are only fooling themselves.

It's clear that his aides are shielding Biden from the reality of his condition and the state of the world. Indeed, you can hardly hide from one without hiding from the other They have gone to great lengths to shield him from the fervor of pro-Palestinian protests. For those who might wonder how that could be possible in the modern age, a president like Biden exists in an information bubble. The only information that enters the bubble is supplied by close aides. 

They are zealously guarding the King's keep, preventing anyone from even asking the question about Biden withdrawing from the campaign.

New York Times:

The Biden team views the very question as absurd. The president in their view has an impressive record of accomplishment to run on. There is no obvious alternative. It is far too late in the cycle to bow out without considerable disruption. If he were ever to have opted against a second term, it would have been a year ago when there would have been time for a successor to emerge. And other than someone with Biden in their name, it is hard to imagine who would have enough influence to even broach the idea with him, much less sway him.