President Trump’s return to Washington has tested the bounds of presidential power and set off alarms among Democrats, historians and legal scholars who are warning that the country’s democratic order is under threat.

But a close review of the 2024 election shows just how undemocratic the country’s legislative bodies already are.

After decades of gerrymandering and political polarization, a vast majority of members of Congress and state legislatures did not face competitive general elections last year.

Instead, they were effectively elected through low-turnout or otherwise meaningless primary contests. Vanishingly few voters cast a ballot in those races, according to a New York Times analysis of more than 9,000 congressional and state legislative primary elections held last year. On average, just 57,000 people voted for politicians in U.S. House primaries who went on to win the general election — a small fraction of the more than 700,000 Americans each of those winners now represents.

Increasingly, members of Congress are not even facing primary challenges. About a third of the current members of the House ran unopposed in their primary. All but 12 of those districts were “safe” seats, meaning 124 House members essentially faced no challenge to their election.

The absence of primaries is even more striking in state legislatures. More than three-quarters of those primary races in 2024 were uncontested, according to voting data from The Associated Press.

Lawmakers who do face primaries are often left beholden to a small number of ideologically aligned, fiercely partisan voters — a group all too willing to drag elected representatives to the fringes and to punish them for compromise with the other side.

“Most members of both parties, liberal and conservative, they’re more worried about losing their primary than losing the general election,” said Haley Barbour, a onetime aide to President Ronald Reagan and a former chair of the Republican National Committee.

Competition has been on the decline in elections for both Congress and state legislatures over the past century, according to academic studies. But the meager number of competitive elections in 2024 points to a problem that is far from being fixed, and may be growing worse.

This reality has helped Mr. Trump expand his ranks of loyal lawmakers in Congress and crush nearly all dissent in his party. In recent months, he and his allies have repeatedly wielded the threat of primary challenges to keep Republican lawmakers toeing the Trump line on issues like federal funding and the president’s cabinet nominations.

But the fear of a primary challenge can also twist local politics, where state power brokers and well-funded interest groups can push lawmakers to take broadly unpopular positions.

For example, in Idaho, where just four out of 105 state legislative races were competitive in November, lawmakers declined for six years to consider expanding access to Medicaid. When the issue finally got on the ballot in 2018, six in 10 voters endorsed it.

The lack of competition in elections has contributed to Americans’ cratering trust in government. A recent Times/Ipsos poll found that 88 percent of adults believed the political system was broken and that 72 percent saw the government as mostly for elites. Just 25 percent viewed government as mostly working for the good of the country.

“They’ve lost track of their voters,” Rory Duncan, 65, a Republican and a retired military veteran from Washington County, Md., said of his local government. “They’ve gerrymandered everything. We used to have a Republican, but they’ve gerrymandered it so much that there’s no way a Republican can get elected.”

Far fewer Americans vote in primaries than in general elections. Last year, roughly 30 million voters cast a primary ballot in a congressional election (that figure does not include Louisiana, which has a unique primary method). The total turnout in the general election was more than 156 million.

Uncontested and low-turnout primaries plague both red and blue states. In Georgia, a battleground controlled largely by Republicans, 10 of the state’s 14 members of the U.S. House did not face a primary challenge. In deep-blue New York, 21 of the state’s 26 House members ran unopposed in their primary.

Incumbency still gives politicians a huge advantage come election season. But incumbents are increasingly tempting targets for primary challenges because those races are largely ignored — making it easier to mount an outsider campaign that targets a few faithful voters.

Of the 59 House members who have lost re-election contests since 2020, nearly half — 28 — were defeated in primaries. In state legislatures, more incumbent lawmakers lost re-election in the primaries than in the general election last year, according to the political database Ballotpedia.

“One thing incumbents worry about is that it’s pretty easy for someone who doesn’t like you to pull together a super PAC and get money,” said Robert G. Boatright, an elections scholar at Clark University, in Worcester, Mass., who in 2013 literally wrote the book on congressional primaries.

Two decades ago, Mr. Boatright said, incumbents lost primaries because of scandal, age or national issues that overrode local loyalties. Today, they are felled by ideological opponents or issue-oriented interest groups often backed by wealthy patrons or legions of small donors with few ties to the races they are financing.

For much of the 2010s, one of the most powerful forces in Texas politics was a group called Empower Texans, the political project of a handful of oil-and-gas billionaires. The group’s political action committee poured millions into replacing more moderate Texas Republican politicians with social conservatives, generally by backing insurgents in primary races.

Though the group’s track record was spotty, Texas politics today is dominated by right-wing leaders, like Lt. Gov. Dan Patrick, who were early beneficiaries of its millions.

On the left, groups like Justice Democrats have had an outsize impact by almost exclusively backing more progressive working-class candidates against more traditional Democrats in a relative handful of carefully chosen primary contests. The group’s first slate of candidates in 2018, funded largely with small contributions from donors nationwide, included Alexandria Ocasio-Cortez, a Democratic Socialist who ousted a 10-term incumbent in that year’s primary and who has since become one of the most prominent House Democrats.

While the Justice Democrats believe they are pushing the party’s centrist policies to the left, extremism is not simply a matter of liberals versus conservatives, according to the group’s communications director, Usamah Andrabi. “Our primaries are not left versus right. They’re bottom versus top,” he said. “If we have to scare corporate politicians into fighting for working people, then they should be scared.”

Nevertheless, Steven Rogers, an expert on state politics at Saint Louis University, in Missouri, said politicians who edged closer to the political fringes were less likely to face primary challenges.

“It’s becoming increasingly clear that over time, more extreme candidates are winning at both state legislative and congressional levels,” he said.

A mirage of meaningfulness

Even contested primary elections can sometimes be a mirage, offering little threat to an incumbent or to the candidate in a state’s dominant party.

Michael Podhorzer, a strategist and the former political director of the A.F.L.-C.I.O., recently analyzed election data to determine how many state legislative primaries last year were competitive and “meaningful” — decided by 10 percentage points or fewer, and with the winner prevailing in the general election.

He found that in the 35 states that held elections for both state legislative chambers last year, just 287 of more than 4,600 primaries met that definition.

That leaves many voters without real representation: The districts that did not have meaningful primaries or general elections last year have roughly 158 million citizens, Mr. Podhorzer said, while those with meaningful primaries have only about 10 million.

Experts are quick to point out that beyond gerrymandering, the political “sorting” of like-minded voters moving into the same communities has exacerbated the lack of competition.

Linda Sacripanti, 58, a Democrat who lives in the deep-red northern panhandle of West Virginia, has experienced both of these political realities.

Participating in primary elections, she says, simply means that “I have some choice in which Democrat is going to lose.”

But for roughly 20 years, Ms. Sacripanti, who works in sales, lived in North Carolina, near Charlotte. She recalled voting for Jeff Jackson in Democratic state legislative primaries, when Mr. Jackson represented a deeply blue district in the State Senate. He parlayed that into a run for Congress in 2022, winning a similarly blue seat by 18 points.

“Charlotte itself is pretty, pretty blue, so my vote had even more weight during the primaries,” Ms. Sacripanti said. “So I do think that it mattered.”

In early 2024, Republicans in North Carolina won a legal challenge that allowed them to redraw the congressional and state legislative maps, wiping away Mr. Jackson’s district and effectively forcing him to resign (he is now the state’s attorney general). Last year, only 10 of the state’s 170 legislative seats had a meaningful primary, including just a single State Senate seat out of 50, according to data from Mr. Podhorzer.

“It was just, ‘Change up the districts and get him the heck out of there,’” Ms. Sacripanti said. “When you look up ‘gerrymander’ in the dictionary, it goes right to North Carolina.”