We'll see, I haven't seen any polls but with the media I would bet they could get Gretchen Whitmer 100% name recognition in weeks, and I would be she would out poll Biden. Add to her ticket a White male Dem with some experience and we have real opposition and they will be able to campaign, unlike Biden.
Again, she is no superstar... yes she has name recognition, but that does not a national winner make. Yes you can get someone who will poll better that Biden, but that doesn’t mean they can win.
Replacement of Biden, particularly at a late date, is effectively an admission the WH is likely lost, and they are desperate to save the down ballot.
The Dems do not have a superstar, and they know it, if they did they would have never allowed Biden to run in the first place.
We shall see.