What about the governors? They have relevant executive experience, and they can’t be credibly tied to Biden. Would they be considered seriously by the convention?
The two obvious options are Gavin Newsom and Gretchen Whitmer. The former is something of a national figure, is more moderate than one might think at first glance, and gives every indication of wanting the job. The latter faced down some really extreme MAGA forces in a very important swing state that could decide the election. She has a reasonable case, too.
But neither has ever run a national race. Neither has been subject to the kind of media scrutiny that comes with a presidential campaign. Newsom has the additional disadvantage of governing a state with image issues in much of America. While both of them are more energetic and charismatic than Biden, is either of them really an improvement?