best track record of any top pundit in the US

The study linked to meant next to nothing in my eyes. It studied political predictions in an election year by political hacks on tv. 2007-2008. Guess what? IN an election cycle that liberals beat conservatives, the liberal predictions more often came true than conservative predictions.

Reminds me of the reported models of mortgage securities, created using data from boom times only.

Krugman was competing with a bunch of other political hacks and columnists. I doubt that accuracy is the highest motivation for any of them. The political hacks want to curry support, and the columnists want to be invited on tv and have their articles read. I'd put at least 3 motivations above accuracy for that crowd: manipulate attitudes, throw red meat to their natural markets, and entertain. It's Dark Arts, all the way, all the time.