A good article, with valid criticisms.
I have already acknowledged that McCain voters probably would stink up the joint just as badly.
If you look at the Pew poll referred to in the WSJ article, it's evident that political knowledge tends to improve if someone is interested in politics, and that the effect is bipartisan.
To be fair, I think this has less to do with intelligence than time available to spend on things like this. People with actual lives don't always have time to wonder who the minority leader in the Senate is.
Link to the actual poll.