As I said last week, the notion that the Democrats are somehow as radically ideological as Republicans is nonsense, and the data is so overwhelmingly indicative of the complete opposite of Peter Wehner's accusations that it almost proves just how radically conservative the GOP has become in the last 40 years.
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 votingdeveloped 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. The chart below, taken from the most recent slice of their data released just last month, illustrate this pretty clearly:
In other words, House Democrats are almost as liberal as they were in the 1920's, and have been drifting back towards that level since WW II after a sharply moderate turn during the Great Depression. House Republicans on the other hand have been skyrocketing towards radical conservatism since the Carter administration.
That's not the shocking part. This is the shocking part.
Some 90% of Republicans are partisans, with 10% moderates (or squishy, traitorous RINOs are they are called in 2015.) 90% of Democrats are in fact moderates, precisely the opposite. And again, House Republican radicalism skyrocketed since 1976 or so. If anything, from Eisenhower through Kennedy, Johnson, Nixon and Ford the Republicans had a higher percentage of moderates than the Democrats.
This is why our Congress is broken and has been for basically my entire lifetime.