Olympia Snowe's surprising retirement announcement has set off yet another round of handwringing about the polarized state of our political system. And as predictable as the laments about why we can't find more common ground is the almost universal presumption in the mainstream media that both sides are equally responsible for the current state of affairs.

Illustrative of the realities of political polarization has been coverage of Snowe's work on health care reform. Though news reports have highlighted her efforts to "work across the aisle" on the issue, they've downplayed the fact that she ultimately voted against a legislative package that, in many of its key features, was drawn up by the conservative Heritage Foundation and represented what was a respectable position within the Republican Party on health care just a few years ago but is now vilified as a sinister, socialist assault on our liberty.

Snowe's ultimate position on health care reform reflects a larger fact about polarization in America that the mainstream media is loathe to acknowledge - that it is highly asymmetrical. A few weeks back, in his widely discussed New Yorker piece on President Obama's political evolution, Ryan Lizza noted that, since 1975, Republicans in the Senate have moved twice as far to the right as Democrats have to the left, based upon the most comprehensive database in political science for evaluating officeholders' ideological positions. And in the House, Republicans have moved six times farther to the right than Democrats have moved to the left since 1975. That same database, the brainchild of Keith Poole and Howard Rosenthal, scores Obama as the least liberal Democratic President since World War II. Funny that, given the endless histrionics from across the right-wing universe about the Kenyan socialist revolutionary who is said to occupy the Oval Office. Emblematic of the extraordinarily reflexive habits of mind of the mainstream media Lizza, having already acknowledged data that shows polarization skews clearly to the right, later analogized that though American politics is normally contested between the forty yard lines (i.e. it's historically been a moderate's game), the parties have now each retreated to their own ten yard lines. How that squares with the skewed realities of polarization previously noted, the author never explains.

There are several factors that explain and reflect this skewed polarization. As Marc Hetherington and I argued in Authoritarianism and Polarization in American Politics, political conflict in the last two decades has come to be dominated by opposed worldviews, based on fundamentally different personality types. Individuals scoring high in authoritarianism have increasingly migrated to the Republican Party and now comprise a decisive part of the GOP's base, whereas the substantial number of Republicans who were low authoriarians twenty years ago have largely left the party. Those high authoritarians who now comprise the core of the GOP are intolerant of ambiguity and have a much greater need to see the world in black and white terms; are suspicious of out groups that they see as a threat to the social order, such as gays, immigrants, Muslims and so on; and are far more likely to process information selectively to conform to their worldview. These findings, which are powerfully supported in a wide range of studies, including ours, are consistent with broader findings about the contemporary right in America. For example, polls show that those on the right express far less willingness to compromise than do moderates and liberals. And as Chris Mooney has been writing about for years, Republicans have engaged in a wide-ranging war on science consistent with American conservatives' growing rejection of and antipathy to widely accepted facts, scientific and otherwise. This is reflected in the construction on the right of an entire alternative information universe, one in which facts are repeatedly distorted and conspiracy theories repeatedly trumpeted.

In sum, the GOP base today is 1) now dominated by folks who are intolerant of many different kinds of out groups 2) unalterably hostile to science and 3) contemptuous of compromise. In those areas of American life in which the public has clearly shifted in a more progressive direction in recent decades, on issues like expansion of health care, gay rights and women's reproductive rights, today's GOP is fighting an evermore full-throated battle to reverse the sands of time. By contrast, where the center of gravity of American politics has shifted to the right - on war and peace, the erosion of civil liberties and the metastasis of our national security state and in terms of tax policies that favor the wealthy - the Democratic party has either eagerly signed on or largely capitulated.

The Olympia Snowes of the world can complain all they want about the lack of middle ground. And the mainstream media can continue to whine about a lack of bi-partisanship. But these plaints misapprehend fundamentally the dynamics of American politics. Right-wing extremism has gone mainstream in today's GOP and not just via the Tea Party, as is evident almost every time Rick Santorum opens his mouth or Romney repudiates yet another of his formerly moderate positions. We're polarized largely because one party has simply gone off the deep end.

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