In Chapter 3, we generated several predictions about how bias and responsiveness in a state's congressional elections should vary as a function of the political context obtaining when the state's district lines were drawn. In this chapter, we put those predictions to the test.

Substantively, we focus on how redistricting in the 1960s affected the partisan outcome of nonsouthern congressional elections. The conventional wisdom is that redistricting is unlikely in general to produce net partisan gains nationwide. Moreover, previous studies of the 1960s in particular have either found no net partisan advantage for either party or claimed that the advantage lay with the Republicans. Nonetheless, we show that nonsouthern Democrats were substantial net beneficiaries of redistricting in the 1960s. Our results explain a long-standing puzzle in the literature on congressional elections: the sudden disappearance of pro-Republican bias in the translation of votes into seats in nonsouthern elections circa 1966.

The rest of the chapter proceeds as follows. We first review work on “the case of the disappearing bias” and consider whether redistricting might help explain this mystery. We then test our theoretical expectations about redistricting – derived in Chapter 3 – against the empirical record in the 1960s. Unlike several previous studies of postwar redistricting, we find that a model in which parties are the key actors explains the data well and that control of state government typically translated into substantial redistricting gains for a party throughout the period prior to the reapportionment revolution. We also find that the legal reversion (or default outcome) of the redistricting process had a systematic and thus-far-neglected impact on how congressional votes translated into seats prior to Baker v. Carr and Wesberry v. Sanders.