Bradley Spahn

Ph.D. Candidate,

Stanford University Department of Political Science




Bradley Spahn is a Ph.D. Candidate in Stanford's Department of Political Science and a dissertation fellow at Stanford's Institute for Research in the Social Sciences, where he studies American Politics and Political Methodology. His research uses voter file data to describe structural features of the American Electorate and improve survey methodology.

His book-style dissertation, "Before The American Voter," draws on 60 years of voter file data from the California Great Registers, spanning the period 1908 to 1968. The data, developed in collaboration with, is the first representative data set covering politics before the New Deal. Consisting of over 57 million voter records matched to the census, the data follows the partisan dynamics of millions of individual California voters over time, exploring political behavior before the advent of surveys.

He uses this data to describe unique features of mass politics from 1908 to 1968. He finds that fundamental features of American political behavior like partisan stability and differentiated partisanship on the basis of class and ethnicity are historically contingent, emerging out of the New Deal Realignment. His research marshals the first direct evidence that the New Deal realignment was caused by the mass conversion of Republicans into Democrats, settling a long debate about whether the mobilization of new voters or the conversion of existing partisans accounted for the Democrats' huge gains in the 1930's.

In other work, he shows how commercial voter files used by campaigns directs voter mobilization activities away from historically underrepresented groups, exacerbating long-standing political inequalities. He has also made contributions to survey methodology, decomposing the turnout bias in the ANES and Pew American Trends panel into its component sources of bias. These studies mark the first decompositions of turnout measurement error in surveys into its constituent parts and the only causally-identified evidence of a mobilization effect for survey-takers.

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Before The American Voter

The stability of party affiliations and the existence of social cleavages between the parties are taken for granted as two fundamental features of American political behavior. But an examination of individual voter behavior shows that these features are historically contingent, emerging out of the New Deal realignment. I examine the impact of the Great Depression on party identification using a new dataset, the California Great Registers, voter lists documenting 57 million California voter registrations for the first half of the twentieth century, matched to census records covering the same period. Pre-realignment, political affiliation was fluid: 10% of voters moved back and forth between the parties each cycle. But after six years of partisan upheaval, party membership stabilized: fewer than 2.5% of voters changing their party affiliation every four years. Early in the century, party and social class were unrelated, but the realignment forged a Democratic-majority among blue-collar workers, while most white-collar workers remained with the GOP. Social cleavages like age, race and national origin only began to map onto partisanship in the 1930’s, indicating that the modern period of stable partisanship characterized by voting in groups is historically contingent, emerging out of the 1930’s


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