That's surprising. His electoral record as Governor is pretty weak. And his wife suffered such severe depression that he considered quitting.
Very true: 20% in '06 with a strong Independent candidate, 6% in '10 with an even stronger Independent candidate. Very weak for a Democrat in Massachusetts.
I doubt that would relay on the national stage though, his demographics make up for his electoral shortfalls.
Governorships are a bit different than Senate elections, and Patrick faced two fairly well-funded and known Republican opponents. After all, Republicans held the Governorship for 16 years before Patrick, so they had a pretty good holding.
He got less than 50 percent running for reelection in one of the most liberal states in the country, beating his Republican opponent by six points.
If a Republican had a similar record in Tennessee I'd be worried about his prospects as a presidential contender.