Rodney Frelinghuysen, Powerful House Republican, Announces He Will Not Seek Re-Election

United States Representative Rodney Frelinghuysen, a Republican from New Jersey who is chairman of the powerful appropriations committee, delivered another blow to Republican efforts to hold onto the House in 2018 on Monday after he announced that he would not seek re-election.

With Mr. Frelinghuysen’s decision to retire at the end of his term, which party leaders for months had feared was a possibility, he became the latest prominent Republican to head for the exits this year ahead of what party strategists worry could be a brutal fall election. Among those are eight who lead some of the House’s most powerful committees.

Mr. Frelinghuysen, 71, did not give a specific reason for not running, but he was likely to face the stiffest challenge in his nearly quarter-century occupying his northern New Jersey seat and his departure gives the Democratic Party a better chance of winning the seat this fall.

Thomas M. Reynolds, who ran the national campaign arm of House Republicans in 2004 and 2006, said he tapped out a succinct email to a colleague upon hearing the news: “Wow.”

Mr. Reynolds said the retirement of a sitting chairman of the appropriations committee, which has long been one of the most sought-after and powerful posts in the House, is highly unusual. Mr. Frelinghuysen was eligible to serve as chairman until 2023.

“It’s an attention grabber,” Mr. Reynolds said in an interview. “Republicans will try to put some sort of a decent face on it but this was not good news for Republicans.”

Mr. Frelinghuysen is the 40th Republican to have left or to announce plans to leave the House, either through retirement, to join President Trump’s administration or to run for another office. Some of those unexpectedly open seats have boosted Democratic hopes of winning the two-dozen seats they would need in 2018 to wrest back control of the chamber.

Though New Jersey’s 11th district has been held by Mr. Frelinghuysen for more than 23 years, and had once been represented for two decades by his father, shifting demographics and political currents in the affluent and suburban area suggest that the Democratic Party may be ascendant.

In 2016, Hillary Clinton lost the district by a single percentage point to Mr. Trump. In 2012, Mitt Romney won the district by five percentage points. The Cook Political Report, which rates congressional races, had already labeled Mr. Frelinghuysen’s re-election prospect a “toss up.”

Mr. Frelinghuysen was facing a challenge from Mikie Sherrill, a former Navy pilot and federal prosecutor, who has the backing of four key Democratic county chairs. And a new super PAC, NJ 11th For Change, was established to help organize a grass-roots effort to unseat Mr. Frelinghuysen.

The group has been relentless in their efforts, holding regular protests outside Mr. Frelinghuysen’s offices and flooding social media with critical messages. And Mr. Frelinghuysen had not been acting like a candidate girding for what was shaping up to be the battle of his political career. He had not been aggressively fund-raising and he has avoided holding town hall meetings.

Still, Mr. Frelinghuysen would have made a formidable candidate — he has decades of name-recognition and nearly $1 million in the bank. Now, whoever ends up being the Republican candidate will be starting from scratch financially even as Democrats in the district have raised hundreds of thousands of dollars.

Ms. Sherrill had nearly $500,000 in the bank as of last September, and is one of 18 candidates across the country that the Democratic Congressional Campaign Committee has selected to support as part of its “Red to Blue” initiative.

Though Mr. Frelinghuysen had shown signs that he might not run, his decision still caught party leaders by surprise and they quickly got to work trying to identify potential replacements.

For New Jersey, Mr. Frelinghuysen’s retirement means the loss of someone who could direct resources to the state. Mr. Frelinghuysen has been a strong advocate for one of the region’s most important infrastructure projects, a new rail tunnel under the Hudson River. He had also been instrumental in steering about $900 million to replace the Portal Bridge near Newark, a key piece of the Northeast Corridor that is prone to malfunctions.

Mr. Frelinghuysen has often been caught between the direction of the party and the desires of his home state. He voted against the federal tax law, citing the harm it would inflict on many of his constituents by limiting the deductibility of state income taxes and property taxes. His vote reportedly angered Republican leadership, and Paul D. Ryan, the House speaker, threatened to strip Mr. Frelinghuysen of his leadership role.

He also initially opposed Republican-led efforts to repeal the Affordable Care Act, before changing his vote at the last minute.

At a time of deep polarization, Mr. Frelinghuysen sought to strike a more moderate tone, saying in his statement that he has striven to reach across the political aisle.

“I have worked in a bipartisan manner,’’ he said, “not just in times of crisis but always, because I believe it best serves my constituents, my state and our country.”

Mr. Frelinghuysen, whose father spent two decades in Congress, was once seen as nearly untouchable in his district. In 2000, the liberal filmmaker Michael Moore mockingly tried to run a ficus tree against him, in a symbol of how little competition there was at the time.

But Mr. Frelinghuysen is the second New Jersey Republican to announce his retirement during the current election cycle. Representative Frank LoBiondo left office in November and his seat is also considered a tossup by the Cook Political Report.

For now, New Jersey Republicans hold five of the state’s 12 House seats, but 11 of the races are considered potentially competitive in November. Mr. Trump won more than 55 percent of the vote in only one of those districts in 2016.

While he may be retiring, those who opposed Mr. Frelinghuysen are not claiming victory yet.

“What we do next, we still have the same mission,” said Elizabeth Juviler, a board member of NJ 11th for Change. “We just don’t have the same target.”