It’s not a stutter, of course. There seems to be 2 factions in the Democratic Party right now. James Carville is in the dump Biden faction, & claims they’ll win. I have no idea which faction will win. thehill.com/homenews/cam...
Considering the technical and legal and financial reasons why dumping him wouldn't work, and the fact they'd have to pick from others who couldn't beat him in the first place, it seems unlikely that Carville's head is still in reality.