Stupak got a bad bounce from Obamacare

The Upper Peninsula of Michigan is a culturally conservative area that viewed most aspects of the health care bill with suspicion. In 2000 and 2004, the district went easily for George W. Bush, and Barack Obama barely managed 50% of the vote there in 2008. Mr. Stupak is known to have taken a private poll of his district since his health care vote, and his retirement announcement is a likely indication that he feared he might lose to a Republican challenger this fall.

Whatever political bounce Democrats thought they would get from passing health care isn't showing up in national polls. In districts like Mr. Stupak's health care appears to be a distinct liability.