The Reapportionment Revolution and Bias in U.S. Congressional Elections

We develop a simple formal model of the redistricting process that highlights the importance of two factors: first, partisan or bipartisan control of the redistricting process; second, the nature of the reversionary outcome, should the state legislature and governor fail to agree on a new districting plan. Using this model, we derive various predictions about the levels of partisan bias and responsiveness that should be observed under districting plans adopted under various constellations of partisan control of state government and reversionary outcomes, testing our predictions on postwar (1946–70) U.S. House electoral data. We find strong evidence that both partisan control and reversionary outcomes systematically affect the nature of a redistricting plan and the subsequent elections held under it. Further, we show that the well-known disappearance circa 1966 of what had been a long-time pro-Republican bias of about 6% in nonsouthern congressional elections can be explained completely by the changing composition of northern districting plans. We thank Michael Alvarez, Chris Den Hartog, Rod Kiewiet, Mike McDonald, Jonathan Nagler, Tom Palfrey, and participants in seminars at Stanford, the University of Minnesota, and the University of California at Riverside for their helpful comments. We also thank Chris Den Hartog for research assistance. For research support, Jonathan N. Katz thanks the John Randolph and Dora Haynes Foundation Department of Political Science, University of California, San Diego, La Jolla, CA 92093-0521; GCox@weber.UCSD.Edu Division of the Humanities and Social Sciences, California Institute of Technology, Pasadena, CA 91125; JKatz@golem.Caltech.Edu, (626) 395-4077. The Supreme Court’s landmark decision in Baker v. Carr (369 U.S. 186, 1962) – holding that state legislative apportionments were justiciable – unleashed a flood of litigation that engulfed all but 14 states within the year. Using several of these cases as vehicles to clarify its substantive position, the Court affirmed that the votes of all citizens must count equally, a position that implied equality of population between legislative districts. In Wesberry v. Sanders (376 U.S. 1, 1964), the Court extended its “one man, one vote” principle to cover congressional elections. The practical result of this flurry of Court decisions and litigation was a massive redistricting effort throughout the country, as state legislators redrew both their own districts and their states’ congressional districts in order to eradicate the substantial levels of malapportionment that then existed. Five states redrew their congressional districts between the time the Wesberry decision was handed down in February and the 89th Congress was elected in November 1964. The main attack on malapportionment, however, was launched after the 1964 election – with twenty-four states redrawing their congressional districts before the 90th, seventeen before the 91st, and six before the 92nd Congress. In this paper, we develop a general model of the redistricting process in the American states and apply it to the study of the reapportionment revolution. We focus in particular on how redistricting in the 1960s affected the partisan outcome of nonsouthern congressional elections. The conventional wisdom is that redistricting (whether in the 1960s or not) is unlikely to produce net partisan gains but 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 paper proceeds as follows. We first review previous work on “the case of the disappearing bias.” We then present a model of the redistricting process, deriving hypotheses about levels of partisan bias and responsiveness under different constellations of partisan control of the redistricting process and reversionary outcome. After reviewing the literature on whether 1960s redistricting plans were partisan, incumbent-protecting, or neither, we suggest why these plans should have benefited northern Democrats. In section 4, we apply our model to congressional redistricting action from 1946 to 1970. Section 5 tests our theoretical expectations against the empirical record. Unlike previous studies, we find that a model in which parties are the key actors explains the data well and that control of redistricting produced substantial gains for the redistricting party throughout this period. Moreover, our results explain the disappearance of proRepublican bias in nonsouthern elections in the mid-1960s. Section 6 concludes. We define as nonsouthern all states not in the former Confederacy. We shall also refer to these states as “northern,” although they of course include western, mountain and border states in addition to the states that traditionally fall under the rubric of “northern”.