Their response has been surprisingly muted thus far. So much of the campaign has been based on going after Biden’s age, infirmity, etc. With him out that messaging is suddenly not just irrelevant but actually now a liability. Even much of their limited anti-Harris messaging so far has been to tie her as directly as possible to Biden, but I don’t think that’ll sway swing voters.
Trump is already suggesting the September debate is off. I think he’s a lot more skittish about sharing a stage with Harris than he would have been with Biden… And he should be. She was a generally succesful courtroom prosecutor, and his personal and legal history, especially of late, leaves him open to a lot of blows.
She has yet to pick a VP running mate, but requests for vetting info have gone out to several potential candidates.
Overall, I don’t think the Republicans are at all pleased with this turn of events. Someone more astute than I described them as “the dog that caught the car”.
I maintain my belief that this is going to be an unusually ugly campaign.