I said in 2006 that the reason why Republicans lost control of Congress is that, when faced with a choice between a Democrat and a Republican trying to act like a Democrat, voters will choose the authentic item almost every time. That apparently applies within the Democratic bloc of voters as well.
That’s true in the 2010 Pennsylvania race for U.S. Senator, and was true in the 2008 race for President.
In my opinion John McCain is “a Republican trying to act like a Democrat”, and even though Sarah Palin is “the authentic item” of a Conservative, she couldn’t overcome the McCain factor. McCain stupidly supported TARP, and led many Republicans to follow his lead into the TARP trap.
Voters who were matching John McCain vs. Barack Obama didn’t see much of a difference, and chose a Democrat over a Republican trying to act like a Democrat.