Judge Posner and Political Polarization

In a recent interview with NPR, Judge Richard Posner said that changes in the contemporary Republican Party has made him “less conservative.”

Below, we use DW-NOMINATE Common Space scores to plot Judge Posner’s ideological location compared to the parties in Congress over the last forty years (the 92nd, 102nd, and current 112th Congresses). This is possible thanks to the work of Lee Epstein, Andrew D. Martin, Jeffrey A. Segal and Chad Westerland, who have developed Judicial Common Space scores (JCS): estimates of the positions of justices and judges along the liberal-conservative ideological dimension which are directly comparable to DW-NOMINATE Common Space scores for members of Congress and presidents.

Judge Richard Posner’s JCS score is 0.034. Interestingly, this places him between two Senators who also became alienated from the Republican Party: Senator Jim Jeffords (Vermont), whose Common Space score is 0.009, and Arlen Specter (Pennsylvania), whose score is 0.070. Of course, both Senators left the Republican Party – Jeffords in 2001 to become an independent and Specter in 2009 to join the Democrats. Of course, in an era of expanding polarization, partisan alienation is not one-sided, seen most recently by former Rep. Artur Davis’s (D-AL) switch to the Republican Party (his Common Space score is -0.29) and prominent Democrats who have stated they will not attend their party’s convention or endorse President Obama for re-election.

A spatial perspective helps explain Posner’s discomfort with the contemporary Republican Party. The below plots show Posner’s location (which is constant) to the distribution of the parties across three Congresses spanning forty years – the 92nd 102nd, and 112th Congresses. Posner has always been on the moderate/liberal wing of the Republican Party, but has become more isolated over time. In the 92nd Congress (1971-1973), between 8 and 9% of Republican members of Congress were more conservative than Posner. This figure dropped to 2-3% twenty years later in the 102nd Congress. Today, Posner would be the least conservative member of the Republican caucus in either chamber. Using Common Space scores, the next most moderate member – Senator Olympia Snowe (R-ME) – is about 0.05 units to the right of Posner.

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