I absolutely agree that he should not have run again. I don't know know much about the dynamics of the race/district, but I see no reason to disbelieve this poll given that CD got a very similar result.
Sherwood's district is a pretty rural one that avoids the industrial slums that Bush carred by 20%. It has rather down to earth folks, who still think like most folks did back say in the 1950's, and far fewer do now, that simply isn't cosmopolitan enough to have tolerance for older man maintaining a mistress on the side. It is a very long way from Paris. I once had a client who lived in Paris, who told me that he didn't trust any politician that did NOT have a mistresss. Paris is not located in the 10th district of Pennsylvania.