There are aspects of contemporary U.S. politics that mainstream pundits and analysts have trouble facing squarely. One of them is the radicalism of today’s Republican Party, not only in terms of policy but at a deeper level, the level of personality and worldview. There’s a two-part story to tell about this.

The first part has to do with the roots of ideology in psychology, brain science, and genetics. To what extent are our political beliefs determined by inherited personality types, brain structures, and even DNA? This has been the subject of a lot of interesting scientific work over the past decade.

Chris Mooney points us to some recent research in The Journal of Politics that traces ideological differences all the way to specific sets of genes. That kind of stuff is obviously tentative and early. A somewhat more robust set of studies traces those differences to structures in the brain. And the evidence for the existence and heritability of divergent personality types is solid.

John Jost of New York University has been studying the psychological roots of ideology for years. In the early 2000s, he did a “meta-analysis” of 40 years of psychological studies on ideology, and in 2006 published “The End of the End of Ideology” [PDF]. As he put it in a subsequent study [PDF], “personality differences between liberals and conservatives are robust, replicable, and behaviorally significant, especially with respect to social (vs. economic) dimensions of ideology.”

What are those differences? What Jost and others have done is test preferences along several axes: stability vs. change, order vs. complexity, familiarity vs. novelty, and conformity vs. creativity. Obviously individual personalities fall all along a spectrum, but in every case, conservatives tend to prefer the former, liberals the latter.

Preferences for stability, order, familiarity, and conformity add up to a strong propensity for what Jost calls system justification, or “favorable attitudes about the overarching social order.” That is true not only among conservatives who are well-served by the status quo — those with wealth and power — but among those whose individual or group interests are ill-served by the social order.

At the far conservative end of the spectrum one finds the authoritarian personality: extremely hostile to change, intolerant of ambiguity or difference, and highly attuned to established hierarchy.

Which brings us to the second part of the story, about American politics over the past 50 years. There was a time when the personality types I’ve been describing as conservative and liberal were more evenly distributed between the major political parties. There were lots of socially conservative Democrats in the South and socially liberal Republicans in the North.

Since then, the personalities have self-selected along partisan lines. All the bleeding hearts have gone to the Democratic Party and all the authoritarians have gone to the Republican Party. Credit for this sorting process is often given to Nixon’s “Southern strategy,” which used race-baiting to peel off socially conservative Democrats in the South. But it’s a much more complex and fascinating story than that; see historian Rick Perlstein’s brilliant Before the Storm and Nixonland.

It’s crucial to understand where that sorting process stands today, because the result has not been symmetrical. That is what’s so difficult for a “balance”-besotted media to portray. The Democratic Party still contains many small-c conservatives and every variety of moderate; indeed, liberals often feel marginalized within the party and infuriated at its policy choices.

In contrast, today’s Republican Party is now almost entirely dominated by the far-right end of the personality spectrum — that is, by authoritarians. Political scientists Marc J. Hetherington of Vanderbilt and Jonathan D. Weiler of UNC Chapel Hill wrote a book about this: Authoritarianism and Polarization in American Politics. As Weiler put it a subsequent article …

… whereas those with the authoritarian cognitive style used to be more evenly split between the parties, decades of appeals for “states rights” and “law and order,” and against ERA, gay rights and immigration reform have concentrated this particular personality type in the GOP. And the consequence of that decades-long process has been the emergence of a Republican party that is, to a remarkable degree, built on viscera — on appeals to anger and resentment, and a deeply-felt conviction that America is breaking down irretrievably and that the way to stop that process is to demonize and marginalize outgroups deemed responsible for that breakdown. And this is no longer a geographically confined phenomenon, but a fully national one.

Policy arguments are not particularly germane to a party “built on viscera.” To such a party, policy becomes merely an instrument to reinforce the status quo and punish out-groups. The notion that the parties are pursuing similar goals but just have differences about the best way to get there is a chimera. There are no shared goals because there is no shared fundamental orientation, not even a shared set of facts. As Weiler puts it, “policy differences are, to an increasing degree, beside the point in a political system defined by personality-based polarization.” I argued something similar in my posts “Policy in an age of post-truth politics” and “The right’s climate denialism is part of something much larger.”

American politics is polarized, yes, but not parallel. The parties are not mirror images of one another. One is a party of multiple, conflicting worldviews and temperaments, the other increasingly homogenous in its authoritarianism. One party struggles for consensus and compromise, the other views politics as warfare.

That is the essential imbalance in American politics today, which can not be accurately described by a media that takes the equivalence of the parties as an inviolable first principle. But if we don’t understand that imbalance, we can’t understand the bitterness and paralysis of the Obama years. And we can’t get serious about what it will take to meet the challenges ahead.

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