Somehow I missed Eugene Volokh’s post on the whole “conservatives are stupid” kerfuffle. There are a few caveats in order with this use of ANES data:

1. Partisanship is not ideology. While the two concepts are correlated highly in the United States, a “strong Republican” is not necessarily a conservative. (The correlation has improved over time, however, as the South has dealigned.) The ANES does include an ideology item.
2. The partisanship scale used by the ANES has a weird inflection point noted by Larry Bartels several years ago: “weak identifiers” are generally more independent in their behavior than “independent leaners.”
3. Political knowledge is not general knowledge (as Volokh’s correspondent notes). Again, while general knowledge is correlated with political knowledge, the latter is only one component of the former.
4. There are numerous disputes over whether “quiz-type” political knowledge questions properly tap overall respondent knowledge about politics. Read chapter 2 of my dissertation if you need all the morbid details. Read the appendix of chapter 4 if you want to see how various types of questions performed in a 1998 Dutch election survey that uses a larger battery of questions than the contemporary ANES (I suppose the Dutch are more willing to subject themselves to quizzes than Americans, although Delli Carpini and Keeter disagree).

The GSS data cited in this InstaPundit post is more dispositive, although I am not as familiar with the GSS—and there may well be caveats that Prof. Lindgren does not mention or is unfamiliar with.