In the just-posted NRO symposium on Kennedy, Linda Chavez makes a comment:

He was smarter and harder working than many of his detractors gave him credit for being, which made him a far more potent adversary than virtually any of his fellow liberals — and therefore a greater threat to conservatives.

I agree with this. Underestimation explains the success of many politicians. Ronald Reagan and George W. Bush come to mind. Overestimation is the mother of failure, and it may help explain President Obama’s sagging popularity right now.