Below we plot the first dimension DW-NOMINATE Common Space scores of the presidents in the post-war period, which we refer to as the “presidential square wave” due to its shape. DW-NOMINATE is a statistical procedure that estimates the ideological positions of members of Congress based on their roll call voting records. In the Common Space procedure, members of Congress who have served in both the House and the Senate are used as “bridges” to estimate scores that are comparable between the two chambers over time. First dimension scores represent the standard liberal-conservative spectrum in American politics, with increasingly positive scores indicating greater conservatism, increasingly negative scores greater liberalism, and the “0″ position denoting the dead ideological center. Presidents are included in DW-NOMINATE scaling by using their “votes” on a subset of roll calls on which the president announces a position on legislation before Congress (measured through CQ Presidential Support Scores).
We find that President Obama is the most ideologically moderate Democratic president in the post-war period, with a first dimension DW-NOMINATE Common Space score of -0.329. President Lyndon Johnson, the second-most moderate Democratic president in this period, has a score of -0.345. President Obama’s ideological position is estimated from his “votes” (statements of support or opposition) on 282 congressional roll call votes. This amount is somewhat low; for example, President George W. Bush “voted” 453 times during his last term in office. However, it is adequate to recover his latent ideological score.
Among members of the 112th Congress, President Obama is ideologically closest to Rep. Jim Moran (D-VA), whose score is -0.328. President Obama is also proximate to Senators Bob Casey (D-PA, -0.332), Kent Conrad (D-ND, -0.326), the recently deceased Daniel Inouye (D-HI, -0.331), and Jeanne Shaheen (D-NH, -0.317). Among Democratic Congressional leaders, President Obama is to the left of Senate Majority Leader Sen. Harry Reid (D-NV, -0.304), and to the right of House Minority Leader Rep. Steny Hoyer (D-MD, -0.395), Senate Majority Whip Sen. Dick Durbin (D-IL, -0.401), and House Majority Leader Rep. Nancy Pelosi (D-CA, -0.530). Interestingly, President Obama has a nearly identical score to former Senate Democratic Leader Sen. Tim Daschle (D-SD, -0.328), whom President Obama had initially nominated for Secretary of Health and Human Services after controversy over unpaid taxes.
Our results may seem surprising to those who consider President Obama among the most — even the most — liberal president of the post-war era. We would respond with a couple of observations. First, President Obama has tacked to the right on many national security and foreign policy issues. For example, President Obama — who once opposed FISA (The Foreign Intelligence Surveillance Act ) — recently supported and signed legislation a five-year extension of the program. Drone strikes — certainly not a source of liberal enthusiasm, even if vocal opposition from the left has been absent under President Obama — have been central to foreign policy during the Obama administration. Furthermore, while foreign policy issues come up relatively infrequently in congressional roll call voting, they constitute a greater proportion of the votes on which the president (i.e., the commander in chief) announces a position.
Second, personal or symbolic factors are not captured in roll call data. DW-NOMINATE scores are estimated only from roll call voting records, and so perceptions of President Obama — for instance — that he is a polarizing president or is aloof towards Republicans are not considered (though, of course, because congressional Republicans have become increasingly conservative, a wide policy distance from them does not necessitate strident liberalism).
We note that there are other ways to quantify latent ideological positions; for example, research by Adam Bonica indicates that President Obama has a donor base that would place him further to the ideological left. However, based on President Obama’s announced positions on actual legislation, we find that he is closer to the ideological center than any president since LBJ.