Would be a great move for Bush, gives him another senate seat.
Actually, no, the Massachusetts legislature passed a law (overriding Gov. Romney's veto) stating that a special election would be held to fill Senate vacancies, rather than the Governor appointing a replacement. So if Kerry had won, his seat would not have been filled by a Republican, but rather there would have been a special election in the spring, with the Democrats obviously having a good chance of winning it.
OK, so he definitely won't do it. Not that he would have anyway.