I think Sarah Palin, I am not sure. I know he did not endorse McCain
She wasn't on the scene until it was down to the general election -- McCain/Palin vs. Obama/Biden. So obviously he'd support the GOP ticket in that instance, no matter who was on it. I'm talking about an early endorsement -- before or at the very beginning of the GOP primaries. And I found the answer: http://hotair.com/archives/2008/02/05/rush-limbaugh-endorses-mitt-romney/