Until the late 1960s, the numbers of people who called themselves liberal was about equal to the number who called themselves conservative. Then the numbers shifted: ever since the 1970s, there have been about twice as many self-described conservatives as liberals. People's opinions on most specific issues did not become more conservative at this time—in fact, there's been a slow liberal movement on many “social issues.”
I was starting to write a post on this paradox when my attention was diverted by some survey questions from a Gallup/USA Today poll taken in December 2011: “How would you describe the political views of [name]--as very conservative, conservative, moderate, liberal, or very liberal?” They asked this about Barack Obama, the major candidates for the Republican nomination for President, and the respondent. For example, 58% thought Michele Bachmann was conservative or very conservative, 10% thought she was moderate, and 10% thought she was liberal or very liberal (the other 22% said they didn't know). It may seem strange that anyone thought she was a liberal, but studies have found that quite a few people seem to have no idea or an idiosyncratic idea of what these terms mean. If you call a conservative rating +1, a liberal rating -1, and a moderate rating 0, you can compute an overall score for perceived ideological position (among those who gave a rating). In her case, it's (58-10)/(58+10+10)=.62. The scores, from most conservative to most liberal:
The relative ratings of the presidential candidates match up pretty well to the way that most "experts" would place them, except for Ron Paul, who comes in as the second most moderate Republican. Of course, Paul has an unusual combination of positions, and some people who call him a “liberal” may mean “libertartian.” Another noteworthy point is that people rate themselves as closer to all of the Republican candidates than to Obama.
Another way to look at this is by the ratio of (Conservative+Liberal)/Moderate. The ratios:
By this measure, Paul is in the middle of the pack. That is, he doesn't rank unusually low in the number of “moderate” ratings. This is also surprising, since I don't think any expert would call him a moderate. It's possible that people are essentially taking an average—if he's liberal on some things and conservative on others, that comes out to moderate. But if that's the case, it's surprising that some people who recognized that he represented an unusual mix didn't volunteer an opinion like “neither one” or “some of both.” Or maybe some did, but the survey organization pressed them to pick one of the standard categories or dumped them into the “don't knows.”