...new polling shows a significant increase in the number of Americans who describe themselves as liberal and the number of Americans taking liberal positions on issues. Gallup has found the percentage of Americans calling themselves social liberals has equaled the percentage of social conservatives for the first time since pollsters began asking the question in 1999 (when 39 percent identified as conservative and 21 percent as liberal). Democrats are more likely to call themselves liberal and Republicans are less likely to embrace the “conservative” description, opting instead for moderate.

Likewise, Republican pollster Bill McInturff, who conducts the NBC News/Wall Street Journal poll with Democrat Fred Yang, has identified a sudden and unexpected shift in ideology among registered voters; such views have traditionally been stable. In several polls over the past year, he has seen the proportion of registered voters identifying overall as conservative drop to 33 percent from 37 percent and the percentage identifying as liberal increase to 26 percent from 23 percent.

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Why? More research must be done to be sure — but there are theories.

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A third theory, which I find compelling, is that the rise in liberalism is a backlash against the over-the-top conservatism displayed by the tea party movement. The Pew Research Center and others have documented a dramatic increase in ideological polarization within political parties over two decades. The Republican Party has long been dominated by conservatives, and the recent rise in liberalism among Democrats may be a mirror image of that — the beginnings of a tea party of the left.
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