Friday, April 9, 2010

DW-NOMINATE: ideology or solidarity?

When I saw this analysis from Chris Bowers showing Senate Democrats "moving to the left" yesterday and today's follow up that the 60th vote is now more conservative than ever, my initial reaction was to say "maybe, but ...". It's not clear to me that the actual ideological positions of Senators have shifted to the left. Political scientists have traditionally understood postwar American political ideology to have two axes, one for economic issues and another for social issues (first civil rights, but later abortion, school prayer, etc.). Over the last twenty years, the two axes have more or less collapsed into one. At the same time, voting patterns in both houses have become more partisan. Because DW-NOMINATE attempts to orient all Senators on a single axis, a world where there are more pro-life but otherwise liberal Democrats, or pro-choice but otherwise conservative Republicans will result in less ideological median Senators almost by definition. Someone really ought to pick up the damn phone and ask Keith Poole about this ...
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