There are 3 choices. The 3rd choice is not voting or voting 3rd party - almost the same - and it's a real option chosen by just as many eligible voters as choose either of the two main candidates.
I think there are going to be a certain % of libertarians and independents who just plain won't be able to stomach it. They can't lie to themselves anymore and pretend the Republican party is the party of rights when they try so fukking hard to just disregard the vote, pardon their criminals, and co-sign the other protofascist tendencies of Trumpism. Even if they don't go Democrat, there are many of them who aren't going to be as motivated to donate, campaign, or vote as they used to be. And whoever comes next isn't going to have the same cult of personality / QANON / Falun Gong following behind him to offset the loses. Not to mention old folk dying, immigration, and white folk not having kids.
Plus it keeps the Republican party indefinitely tied to Trumpism, and the large majority of young people coming up and becoming new voters just think that's disgusting.