The number of politically competitive U.S. House seats has fallen rapidly in recent years as redistricting, declining ticket splitting and residential sorting combine to produce more safe districts for both parties.
How the map changed
For decades after World War II the number of swing seats — defined as districts a presidential candidate won by 5 percentage points or fewer in the prior election — steadily declined. That long-term trend accelerated over the last year amid a partisan redistricting fight that followed actions by President Donald Trump and state legislatures.
One measure cited in recent reporting shows swing seats dropped from 45 to 37 in the last year. An earlier count from the 1970s found 96 districts met the modern definition of a swing seat in 1964.
Illustrative races
Changes to maps rather than shifts in voter preferences help explain some dramatic swings in outcomes. In North Carolina’s 13th Congressional District, Democrat Wiley Nickel won narrowly in 2022 by about 9,000 votes after running as a moderate. Two years later, the seat was carried into the U.S. House by Republican Brad Knott by more than 70,000 votes.
Republican-controlled lawmakers in North Carolina redrew the district to remove Democratic-leaning precincts in Raleigh and add a swath of rural counties extending toward the Virginia border. The new shape, described by state officials as an hourglass, converted a competitive seat into a safe Republican district.
- Reduced ticket splitting: Voters increasingly cast ballots for a single party across races instead of splitting their ticket.
- Residential sorting: More Americans live in communities with like-minded neighbors, concentrating Democratic voters in urban areas and Republican voters in rural areas.
- Partisan redistricting: State legislatures have redrawn lines that further diminish the number of districts that can change hands.
Political analysts and party strategists have cited all three forces as contributors to the shrinking battlefield for House control. The decline in competitive districts affects campaign strategy, resource allocation and the ability of either party to gain or lose a significant number of House seats in a single election cycle.
Election results and map changes cited in recent coverage provide concrete examples of how redistricting can alter the partisan makeup of districts without widespread changes in voter opinion.
