As I said yesterday I would look at actual evidence as to the relative intellectual ability of liberals relative to conservatives.
A lot of the quantitatively minded science bloggers have used the General Social Survey to get estimates of the relative intelligence of different groups. The variable generally used is the literacy test known as "Wordsum". As are also reasoning questions on there known as "Alike1... Alike8" I have combined them into a variable "AlikeSum" and then created a variable combining both known as "WordAlike".
I have then run "WordAlike" with a variable "PolyViews" which asks people to identify their political leanings.
The mean score for each group (out of 26) is as follows:
Extremely Liberal: 15.01
Slightly Liberal: 15.37
Slightly Conservative: 15.87
Extremely Conservative: 14.7
Total Liberal: 15.41
Total Conservative: 15.61
There seems to be a slight conservative advantage on reasoning and a slight liberal advantage on verbal ability, but I doubt enough to be significant. If anyone has the time or inclination they could roughly translate them to IQ scores but that seems a pointless exercise.