Because McCain as the presidential contender was more conservative and trustworthy than McCain as the Senator. McCain knew he could not win support of the right without choosing someone like Palin, who would have forced him to govern from the center-right.
McCain as a Senator is too liberal and too much of a back-stabber. Sarah has no obligation to support McCain's Senate re-election.
Look, the Tea Party movement is angry at Republican incumbents and statists too. Did Sarah not think McCain was immune from this? If she wanted to repay some perceived debt to McCain, all she had to do is stay out of the primary and then campaign for McCain in the general election.
Yes, that's a good answer, but if McCain asked her for an endorsement, then she could hardly have refused, given what he did for her. There are times when loyalty and gratitude are more important than ideological purity, and this was one of them. Purists can find fault with even the best politician, but Sarah Palin is no RINO.
You wrote, “If she wanted to repay some perceived debt to McCain, all she had to do is stay out of the primary and then campaign for McCain in the general election”
If Sarah Palin was asked by McCain to campaign for him and she turned him down, the MSM and all libs would have a field day.....blasting both McCain and Sarah. They would love that.
When campaigning (hopefully limited) she can choose to only talk about his positions that she herself endorses, and leave out the horse crap things like, “hands across the aisle”, “amnesty”, “campaign finance reform”.
I don't remember McCain being conservative and trustworthy, ever. Sometimes he fools people though.