Most Americans, Krugman says, take clearly "liberal" or "conservative" positions on both economic and social issues. Here's the graphic Krugman drew to represent his claim:

It's correct to say that few Americans identify as libertarian. Only 11 percent said the term "libertarian" describes them well, according to a 2014 Pew Research poll.

Nor do very many Americans self-identify as socially liberal but economically conservative. Just 3 percent did so in a 2012 Gallup poll, in fact. Even fewer Americans — just 1 percent — fall into the category Krugman calls "hardhats," that is, people who are socially conservative but economically liberal.

But how people label themselves is one thing. Americans sometimes leave a different impression when polled about specific issues. Often, their views are reasonably heterodox and not well represented by a one-dimensional political spectrum.

Take two issues that are taken as emblematic of the split between liberal and conservative viewpoints: gay marriage and income inequality. If Krugman is right, you should see few Americans who are in favor of same-sex marriage but oppose government efforts to reduce income inequality, or vice versa.