Why are fewer congressional elections competitive at the district level when the national electoral environment is at its most competitive? This article explores this “pseudoparadox,” and argues that the answer can be found in partisan redistricting. Through an analysis of 40 years of congressional elections, I find that partisan gerrymanders induce greater competitiveness as national tides increase, largely due to unanticipated consequences of waves adverse to the map-drawing party, particularly in seats held by that party. The phenomenon anecdotally coined by Grofman and Brunell as the “dummymander” is thus actually quite common and has significant effects on rates of congressional competition nationally. In contrast, bipartisan maps are shown to induce lower competition, while nonpartisan maps induce higher competition, under all electoral conditions and competitiveness measures. But the effects of partisan gerrymanders on competition, though strong, can only be seen in interaction with short-term national forces.