and there are catastrophic political costs to switching someone other than Harris for Biden.

On this we disagree. Having an open convention would be messy, and at the same time galvanizing television. The Dems do have a bench, and there would be ample opportunity for the obvious contenders (Newsom, Wittmer, Buttegeig, Harris) and perhaps others to make their case and to go through one round, perhaps multiple rounds of voting - as used to happen in the pre-McGovern era.

There is also the possibility that Harris could win, or throw her support to one of the others in return for being assured the #2 slot. Again. If it went past a round or two, I would advocate a floor resolution to move to “ranked choice” voting, which would clear it up relatively quickly.

I don’t know why it would be “catastrophic”. Other countries have election season that last barely weeks; there is no reason ours has to go on for years.