OK Cupid studied a huge subset of their members and came to some really interesting conclusions about Republicans, Democrats, and how Republicans cohere but Democrats don't (also some cool stuff on social/economic views by age, and some really cool graphs, and... oh, just go look at it:)
http://blog.okcupid.com/index.php/2010/03/30/the-democrats-are-doomed-or-how-a-big-tent-can-be-too-big/ Thanks for the link,
melebeth !