Both Palin and Romney chose to support the people who have the best chance of knocking off the democrats in CA, Fiorina and Whitman. And, they were both swayed by, among other things, personal friendship and loyalty.
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.