To sum it up: Barack Obama must visit toss-up seats because in the past districts with Presidential visits had a higher retention percentage than districts without them.
This was one of those posts that ended up rambling: the reasons why this isn’t the game-changer that the author thought it was were all trying to crowd in to get the credit for shooting this one down. Really short version: dice may not have memories, but Congressional districts emphatically do. And the President is not actually capable of performing acts of magic. Or even ‘magick.’
Look, you should have seen what I deleted. Borrrr-ring…
And this is the problem with regression analysis — leads people to confuse correlation with causation. Far more likely is that a POTUS will visit a district where his candidate has a good chance of winning. Not all swing districts are created equally: Bush visiting PA-10 in 2006 would have been quite a bit different than visiting, say, PA-08.