Affirmative Districting and Four Decades of Redistricting: The Seats/Votes Relationship 1972-2008

Abstract

How has the partisan seat/vote relationship in U.S. congressional elections changed in the four reapportionment cycles since 1970? Concern about a biased and unresponsive districting system and "vanishing marginals" has increased because of the affirmative districting to create minority-majority districts after 1990. The 1990 redistricting cycle did not give Republicans an unfair advantage in the seat/vote relationship nationwide or in the southern states, but it may have reduced a previous Democratic bias. The 2000 cycle may have given the GOP a slight advantage. More recent districting cycles with affirmative districting have increased both the responsiveness of congressional elections and the number of opposed contests.

The 2018 Pennsylvania Midterm Election

“…12 Adjusting the vote to account for the unopposed Democratic seat in PA-18 produces a 54% to 46% advantage for the Democrats. 13 This advantage is about the same that Democratic candidates carried nationally, approximately 7 points (Arrington 2019).…”

A Thermostatic Model of Congressional Elections

“…2.According to Brookings, these totals “exclude districts in which candidates ran unopposed and no vote was recorded.” Analyses that attempt to model the likely vote share in these districts if there was two-party competition find similar results (Arrington, 2019), but uncontested seats are important in explaining the timing of the Southern realignment (Wrighton & Squire, 1997). …”