I've listened to Palin, rather than read fairy tales into what she is saying as many have. If you heard her announcement that she is not running, she made it pretty plain her primary goal is defeating Obama - in fact she has clearly said ABO (Anybody But Obama) is the overriding issue in 2012 on other occasions as well. She made clear she was not running as an independent because it would make Hussein's re-election more likely. I am not saying Palin would endorse Romney in the primary process, I am saying she has made it clear she will help the Republican nominee win and there was no exception made for Romney or anyone else. Palin will endorse, support and campaign for the eventual Republican nominee.
As for me, Romney is flip flopping chameleon and one of the least desirable options, but I would most certainly vote for him over Obama. I doubt I could generate much enthusiasm for him (though I suppose if her chose a very conservative VP running mate it could help), but I'd certainly vote for him if he were the nominee. Paul is a clown and has zero chance of winning the nomination (nor does Johnson), so there is no reason to even consider such an event.
I think Palin’s best help would be flushing RINOs in primaries like our Dick Lugar here in Indiana, AND working to build a large majority in the Senate, no matter who is POTUS.