Democrats in New Jersey appeared likely to retain a comfortable majority in the Assembly and the Senate, according to early results from The Associated Press in Tuesday’s races.

“It was a huge night,” said Nick Scutari, the Democratic Senate president. “We had good candidates. That’s why I felt confident going into this week.”

Two years ago, with the state’s Democratic governor, Philip D. Murphy, at the top of the ticket, Republicans gained seven seats in the Legislature. Voters angered by the government’s Covid-19 mandates showed up to the polls in droves, a turnout that many losing Democrats called a “red wave.” Mr. Murphy became New Jersey’s first Democratic governor to be re-elected in 44 years, but he won by just three points.

On Tuesday, all 120 seats in the Democrat-led State Legislature were again on the ballot, and Republicans were hoping to tally further gains.

But as of 11:30 p.m., Democrats had held on to win in competitive districts in southern and central New Jersey and were leading in other key races.

Before Tuesday’s vote, Democrats held a 25-to-15 majority in the Senate and a 46-to-34 advantage in the Assembly; it has been two decades since Republicans had a majority in either house.

Two years ago, the most spectacular loss for Democrats was in South Jersey, where Stephen M. Sweeney, a Democratic labor leader who at the time was the Senate president, lost his seat to Edward Durr Jr., a conservative, first-time candidate.

Late Tuesday, with 95 percent of the vote counted, Mr. Durr, a driver for a furniture store who embraced the nickname Ed the Trucker, was losing to the Democratic candidate, John J. Burzichelli, by six percentage points. Mr. Burzichelli represented the district in the Assembly for 20 years before losing in 2021.

The odds of Republicans overtaking Democrats in the State House were always long.

“We’re close enough to the target,” Alexandra Wilkes, a New Jersey Republican Party spokeswoman, said last week about the possibility about winning a majority in either house, “but we have to hit the darts right every time.”

In Monmouth County, a largely conservative area on the Jersey Shore, three Republican incumbents lost seats, according to the A.P. results.

Shaun Golden, the chairman of the Monmouth County Republican Committee, acknowledged that the candidates had “come up short.”

“Our legislative results are, to put it bluntly, a mixed bag,” he said in a statement.

Much of the campaign rhetoric revolved around cultural wedge issues, including abortion rights and whether schools should be required to tell parents about the way students express their gender. State policies meant to make residents less dependent on gas-powered stoves and vehicles have also been used by Republicans to energize their base.

On Tuesday evening, Senator Andrew Zwicker, a Democrat who was first elected in District 16, near Princeton, N.J., by fewer than 100 votes, was still knocking on doors after sunset in South Brunswick, hoping to persuade residents to vote. During the campaign, he was attacked for legislation he introduced opposing book bans in schools and in support of transgender youth.

Mr. Zwicker, a scientist who works in Princeton University’s plasma physics lab, said he was hopeful that the districts’ residents would “see right through that.”

They apparently did. He beat his Republican opponent, Mike Pappas, a former congressman, by about 12 percentage points.