1)This is speculation from some blog, I doubt Manchin is switiching
2)Bayh? What are talking about? His career is over after he lost last year. He certainly is not primarying Donnelly.
Like Donnelly - whose seat is rated most likely to flip - wouldn't do exactly what he was told to do, particularly in a more favorable electoral environment for Bayh.
Like Greg Pence OR his current protege Messer would be considered to be unbeatable by even Donnelly's friends.
Like losing to Young represents Bayh's one loss in 30 years of wins.