I actually voted in the last election in which a Republican Senator from Massachusetts was on the ballot. I was a first year law student living in the Allston neighborhood of Boston (just accross the Charles from Cambridge). Ed Brooke lost that fall to Paul Tsongas. It's been Democrats ever since.
Tip O'Neill was my Congressman back then and he used to say that all politics are local. But the race between Scott Brown and Martha Coakley is not. It's all about ObamaCare. If it wasn't before the President flew into Boston, it is now.
There is no way for the White House to win this. Even if Coakley squeaks out a victory, a general election for the Senate in Massachusetts is not supposed to be close. Massachusetts will elect a Republican governor, but its national politics are deep blue (although Reagan carried the state twice). If Brown wins, the Blue Dogs will be in revolt. Heck, they may be anyway. The President has to hope the polls are wrong. That seems unlikely.