Politico's Andy Barr:
Responding to speculation that Romney may be interested in the seat—which he challenged Kennedy for in 1994—Eric Fehrnstrom, a spokesman for Romney’s political action committee, told POLITICO that the former one-term governor has no interest in campaigning to replace Kennedy.
“Governor Romney’s focus right now is on helping other Republicans run for office, and that is how he will be spending his time,” he said.
AllahPundit made the case against yesterday:
Obama’s still near 60 percent approval in Massachusetts.... And there’s more to lose in doing this than there is to gain. If he wins, he ends up stuck in the minority with the rest of the GOP with no way to pass legislation unless he compromises with the Democrats — not something a guy who’s already suspected of RINOism is wont to do. If he loses, it proves he’s a paper tiger who can’t even carry the moderate states to which he’s supposed to appeal as a potential Republican nominee.
Besides, in order to get into the White House these days, you have to get out of politics -- that's the way the system works now, at least for front-runners, Pawlenty, Palin, Huck, and Romney.