The Republican/Tea Party has already thrown Scott Brown under the bus. He'll be out in 2012, of course, but it won't be because Obama will be on top of the ticket (O isn't really all that popular in Massachusetts. He lost it in the primary, the swing to him was negligible in 2008, and he didn't really have any coattails for Martha Coakley); it will give the Democrats time to find another candidate "better" than Martha. Hopefully this time they won't take the seat for granted.
As for the win in Hawaii, any generic Democrat will win the seat back in November. It's Hawaii, and a district that native son Obama won with 70 percent of the vote. That'd be like if there was a two-way Republican race in Wyoming and the Democrat squeaked by in a plurality, I would say the same thing, that the seat would flip back GOP just because it's Wyoming.
As for Obama, yeah, it appears that all of his endorsements are toxic. Buyer's remorse, Democrats? 
To be fair, Bush Jr. won 47% in HI-01 in 2004. And even if Obama isn't super-popular in MA, he will get at least 60% of the vote in MA even in a relatively bad year. Thus, he should have enough coattails for a strong Democrat to defeat Brown. As for buyer's remorse, I admit that Hillary would have probably been a better President.
