Actually Palin waited until the last 4 weeks, saw that proabortion/gay marriage, Tom Campbell was breezing to a win, and she stepped in to stop it.
Romney is the guy that mentored Meg Whitman and helped push her to run as a Tom Campbell like liberal, Romney ran Whitman to shut out any conservatives from the primary.
Palin is trying to take the Senate seat and get a more conservative, pro life candidate in, Romney initiated a plan to take over the California Governor's seat and keep it out of the hands of a pro lifer.