Once democrats have a candidate in Mass., the race will get a lot closer. and Kerry, the Kennedys and Obama will be campaigning for him. I don't think Brown will win, specially if republicans nominate a person who isn't romney.
We have seen what Obama campaigning for Coakley or a few other Dems has done.
Zero effect.
It is important to note here that Brown is on extremely good terms with Massachusetts Democrats (read: the ones in political power), from Mayor Menino all the way up to the congressional delegation. I'm not sure why the establishment likes him, but it does. And so long as it does, it's going to be damn hard to get Brown out of office.
PS: With regard to the Kennedy thing ... Massachusetts has moved on. We loved Jack because there was a reason to love Jack. We loved Ted because there was a reason to love Ted. But ... at this point, what exactly does the family have left aside from drunkards, spoiled brats, and a lobbyist for Venezuelan oil concerns?