No, Munchkin committed that treason AFTER the 2012 election. Manchin was actually endorsed by the NRA, and given an "A+" rating in both 2010 and 2012.
I think he's in danger; he will face a primary challenger, and the challenger is almost guaranteed to be even nuttier than he is. I give 50/50 for his re-nomination by the 'Rats, and better than 50/50 for re-election if nominated. WV Republican Party has its collective head up its ass; no clue how to run a statewide campaign.
Capito won in 2014 mainly because her opponent was completely bat-guano crazy, and not well known.
Is there any chance Manchin might be swayed to change parties?