In 1999, there were 164 House districts where election results were within five points of the national popular vote. Today there are only 82. One major factor in the elimination of competitive swing districts is gerrymandering, which could have a decisive impact on which party controls the House of Representatives in 2025.
The Cook Political Report defines swing districts as those in which the election results are within five points of the nation's overall vote. For example, if the national vote is 50% for Republicans and 50% for Democrats, a swing seat would be any seat where the district voted within five points of the national vote in favor of either party. Over the past 25 years, however, the number of competitive districts has been cut in half. Beyond just the shrinking number of total competitive seats, many of the competitive seats are located in just two states: New York and California.
According to Jonathan Cervas, a professor at Carnegie Mellon University and redistricting consultant, redistricting — when states redraw their congressional districts every ten years — is a key part of the decline in competitive House races and has been for decades. Because voters are “not very persuadable,” redistricting has become a “primary method” by which parties can gain or lose seats in Congress, he explained. Since the 2010s partisan redistricting, or gerrymandering, has resulted in relatively few competitive House races.
“It’s much easier for a political party to change district lines to enhance their ability to win than it is to change voters minds,” Cervas said.
Following the 2010 Census, Republicans made a concerted effort to win control of state legislatures, the body that draws district lines in most states. Winning control of those bodies gave the GOP the power to draw more district lines and allowed the party to enact partisan gerrymanders in states like Texas and Utah. In the 2020s, Democrats caught up to Republicans and sought to enact partisan maps in states like New York and Illinois.
The problem, for Democrats, is that two states where they likely had the best opportunity to pick up seats via redistricting, New York and California, have laws preventing them from doing so.
In both New York and California, redistricting is handled by an independent redistricting commission. Although lawmakers in New York attempted to circumnavigate the commission to push through a map that benefited Democrats, courts ultimately struck down the gerrymander and the state adopted maps very similar to those drawn by Cervas himself, who was appointed to draw neutral maps for the state.
This is how the parties ended up with the current situation: few competitive districts with many of them concentrated in just two states, New York and California. While most good government advocates would say that eliminating gerrymandering is a positive development in these states, it could disadvantage Democrats because Republican-led states did not eliminate gerrymandering.
A Brennan Center Analysis of the post-2020 Census redistricting found that because of lopsided gerrymandering, Republicans enjoy an advantage of around 16 House seats due to redistricting alone.
“In terms of gerrymandering it’s sort of a tale of two countries," Michael Li, senior counsel for democracy at the Brennan Center, told Salon.
“There are places where maps are fair and have gotten better and there are places where maps are deeply steered,” Li said. “If you watch the news almost everything is about these seven battleground states, but in terms of toss-up districts only a third of them are in toss-up states.”
Many of the Republicans' post-2020 gains via redistricting came from Texas and Florida. According to Li, Republicans will likely gain five seats in both Texas and Florida as well as two seats in Georgia, North Carolina, Ohio and Iowa. They will also likely gain a single seat in a handful of states around the country. Democrats, on the other hand, will likely pick up two seats in New Jersey and three seats in Illinois because of redistricting, as well as a seat in Oregon and in New Mexico.
Li explained that part of this has to do with different philosophies of district drawing between the parties as well. To gain seats, a party wants to win each seat with as few votes as possible to protect the seat over the ten-year lifespan of a district map a party will want a safer margin.
“When you gerrymander you have to choose between having safe districts and more districts,” Li said. “Democrats are working to make sure that their districts are safe.”
The set of maps this year also differs from the maps used in 2022, with five states adopting new maps in the two years since. Alabama and Louisiana were ordered by a court to adopt new maps that included a new majority Black district in each state after their previous maps were found to have violated the Voting Rights Act.
Georgia was also required to adopt new maps under the Voting Rights Act, though they offset the new majority Black district they were required to include — and which will likely elect a Democrat — by diluting a different Democratic-leaning district.
North Carolina also adopted new maps after the newly elected Republican-controlled state Supreme Court decided to reverse the court’s 2022 ruling against partisan gerrymandering. The decision gives Republicans the edge in ten of the state’s 14 districts.
New York is the final state to adopt a new map, though the new maps don’t give one party or another a distinct advantage in the districts. According to Cervas, the changes since 2022 slightly benefit Republicans but don’t radically change the overall partisan advantage Republicans received from redistricting.
