GOP Congress More Extreme Than Democrats

Christopher Ingraham quantifies the obvious on The Washington Post's Wonkblog.

Political scientists have known for years that political polarization is largely a one-sided phenomenon: in recent decades the Republican Party has moved to the right much faster than Democrats have moved to the left. As Thomas Mann of the Brookings Institution has described it, "Republicans have become a radical insurgency—ideologically extreme, contemptuous of the inherited policy regime, scornful of compromise, unpersuaded by conventional understanding of facts, evidence, and science; and dismissive of the legitimacy of their political opposition."

The data backing this claim up are pretty solid. The most widely-used measure of political polarization, a score of ideology based on voting developed by Kenneth Poole and Howard Rosenthal, has shown that the Republicans in the Senate and especially the House have drifted away from the center far more rapidly than Democrats.

Here's another way of looking at it: How many moderates are in each party? Here's another interesting chart from the Poole-Rosenthal data, showing the number of House members in each party who are not centrists -- that is, whose ideological scores put them on the more extreme ends of the partisan scale.

...in the most recent Congress nearly 90 percent of Republican House members are not politically moderate. By contrast, 90 percent of Democratic members are moderates. It's quite difficult to square a chart like this with a claim that Democrats are abandoning the center faster than Republicans. As the chart shows, there are plenty of centrist Democrats left in the House -- but hardly any centrist Republicans.