Competition is an endangered species in legislative elections.

A New York Times analysis of the nearly 6,000 congressional and state legislative elections in November shows just how few races were true races. Nearly all either were dominated by an incumbent or played out in a district drawn to favor one party overwhelmingly. The result was a blizzard of blowouts, even in a country that is narrowly divided on politics.

Just 8 percent of congressional races (36 of 435) and 7 percent of state legislative races (400 of 5,465) were decided by fewer than five percentage points, according to The Times’s analysis.

Consequences from the death of competition are readily apparent. Roughly 90 percent of races are now decided not by general-election voters in November but by the partisans who tend to vote in primaries months earlier. That favors candidates who appeal to ideological voters and lawmakers who are less likely to compromise. It exacerbates the polarization that has led to deadlock in Congress and in statehouses.

“Because of partisan and racial gerrymandering, you end up with these skewed results and legislative bodies that don’t necessarily reflect the political makeup of either the states or, writ large, the House of Representatives representing the political desires of the American people,” said Eric H. Holder Jr., the attorney general in the Obama administration who, as chair of the National Democratic Redistricting Committee, has criticized the mapmaking process and at times even called out his own party’s redistricting practices.

In 2020, the last time that once-a-decade national exercise took place, both parties largely followed a similar strategy. Their maps typically made districts safer by stocking them with voters from one party, rather than breaking them up in an effort to pick up seats. Republicans, as the party in control of the process in more states, drew more of these slanted districts than Democrats.

Other factors have contributed to vanishing competition, including demographic shifts and “political sorting” — the tendency of like-minded citizens to live in the same community. But the role of redistricting is evident when zooming in on a single state.

Take, for example, Texas, where in 2020, before redistricting, 10 of 38 congressional races were decided by 10 percentage points or fewer. In 2024, just two races were. In five races last year, Democrats did not even run a candidate, ceding the seat to Republicans. One Democrat ran unopposed.

In state legislatures, where lawmakers are drawing maps for their own districts, safe seats abound.

There are 181 state legislative seats in Texas, with 31 senators and 150 representatives. In 2024, just four of those elections — three in the Statehouse and one in the State Senate — were decided by five points or fewer, according to The Times’s analysis.

“Legislatures draw maps in most places, and the reality is, a big concern for members who have to pass these bills is: ‘What happens to my district?’” said Michael Li, a senior counsel for the Democracy Program at the Brennan Center for Justice. “Very few members are willing to say, ‘Oh, gosh, I should have a more competitive district.’ So there is an inherent conflict of interest in the way that we draw districts.”

Adam Kincaid, the director of the National Republican Redistricting Trust, said that making seats safer was always the goal.

“We made no bones about the fact that we’re going to shore up incumbents, and where we had opportunities to go on offense, we were going to do that,” Mr. Kincaid said. “So what that means is bringing a whole lot of Republican seats that were otherwise in jeopardy off the board.”

The Power of a Map

While it is easy to focus on the candidates, the money, the message or the economy, increasingly it is the maps that determine the outcome. In North Carolina, they may have decided control of the U.S. House of Representatives.

Only one of the state’s 14 congressional districts was decided by fewer than five points. A Republican won the state’s next closest race — by 14 points.

In 2022, the State Supreme Court ordered a more competitive map, but it was tossed out after midterm elections shook up the balance of the court. The replacement, which was drawn by the Republican-led Legislature, gave three Democratic seats to the G.O.P. while making nearly every district safer for the party that held it.

It is impossible to know how elections held under the first map would have turned out. But, according to Justin Levitt, a redistricting law expert at Loyola Law School in Los Angeles, “had every seat stayed the same as in 2022, those three seats would have made the difference, and Democrats would have had a one-seat majority” in Congress.

Of course, North Carolina played a pivotal role because the margin in the House was so small. Gerrymanders nudge the political balance in every election, but the 2024 vote was the rare occasion in which they were decisive.

North Carolina’s role in the 2024 House elections follows a historic U.S. Supreme Court ruling in 2019 — involving partisan congressional maps in North Carolina — in which the court called partisan gerrymanders a political problem outside federal courts’ jurisdiction.

Even though those maps were “blatant examples of partisanship driving districting decisions,” the majority wrote, “state statutes and state constitutions can provide standards and guidance for state courts to apply.”

Almost unnoticed, other battles over slanted congressional maps that could affect the 2026 elections are crawling though state and federal courts — in Alabama, Arkansas, Florida, Georgia, Louisiana, North Carolina (again), South Carolina, Texas and Utah.

Of all those lawsuits, the one most likely to affect the next House elections appears to be in Utah, where Salt Lake City, the state’s liberal hub, was carved into four districts to water down the impact of Democratic voters on House races.

Democrats appear likely to pick up a single House seat from that litigation, which faces a crucial court hearing on Friday.

Nationwide Decline

North Carolina is hardly an outlier.

In Illinois, a state dominated by Democrats, no congressional election was within a five-point margin, and just two were within 10 points. In Maryland, just one district was within a five-point margin.

Georgia did not have a single congressional district within a 10-point margin, out of 14 seats. The state’s closest race was the 13-point victory by Representative Sanford Bishop, a Democrat, in the Second Congressional District.

At the state legislative level, the numbers were even starker.

In Georgia, just five of the 236 state legislative seats, or 2 percent, were decided by five points or fewer, and more than half of the races were uncontested. In Florida, 10 of the 160 state legislative races were within a five-point margin.

With so few general elections to worry about, tribalism can take over in legislatures, leaving many elected officials to worry only about primary challenges, often from their party’s fringes. In the modern climate of political polarization, the lack of competitive districts not only removes an incentive to work with the other party but actively deters doing so.

“As competitive districts dwindle, so do incentives to compromise,” said Steve Israel, a former Democratic congressman from New York and the former chair of the Democratic Congressional Campaign Committee. “I remember campaigning on bipartisanship in a very moderate district in my first election in 2000. By the time I left in 2017, talking about crossing the aisle was like announcing a walk to my own firing squad.”