WASHINGTON -- It was supposed to be a game-changer for New Jersey, a state so long absent from having any real power on Capitol Hill.

After waiting for years, Rep. Rodney Frelinghuysen had finally ascended to the chairmanship of the House Appropriations Committee, a panel that truly wields clout because it doles out dollars.

But the big job could cost him dearly back home in New Jersey.

Frelinghuysen's power has ironically weakened him politically as House Republicans have passed unpopular legislation that could hurt New Jersey on health care, taxes and other issues.

"It makes him the face of the Republican agenda to voters of the district," said David Wasserman, House race analyst for the Cook Political Report, a Washington-based publication that rates Frelinghuysen's 2018 re-election chances as a toss-up.

"It used to be that power and incumbency was an electoral shield," Wasserman said. "Now it puts a target on your back."

Unhappy Jersey voters aren't the only ones taking aim. One ex-lawmaker said Frelinghuysen's new-found clout was threatened by House Republicans who want him to vote with the GOP on taxes.

This can't be what Frelinghuysen, R-11th Dist., expected things to be like when he reached the pinnacle of his political career of more than two decades.

"He's got the interests of his state and district and sometimes that's not matching up to what the national interests are," said Rep. Frank LoBiondo, R-2nd Dist., who was elected to the House with Frelinghuysen in 1994. "I don't know how you would expect that."

For his part, Frelinghuysen ticked off a long list of accomplishments for the state. He has worked to get federal funds for the Gateway tunnel project under the Hudson River, for Joint Base McGuire-Dix-Lakehurst, for security at Jewish community centers hit by bomb threats and for preserving the federal program that helps low-income families pay their home heating bills.

He's also rejected President Donald Trump's proposals to end funding for the National Endowment for the Arts, the National Endowment for the Humanities and the Committee for Public Broadcasting.

"I sought the chairmanship of the Appropriations Committee for one reason: to ensure that New Jersey and national priorities are met," Frelinghuysen said.

At the time, "the atmosphere was slight less toxic than it was now," said Ross Baker, a Rutgers University political science professor. "The lines weren't as indelibly drawn."

Such a high-profile position magnifies Frelinghuysen's votes on major issues and puts pressure on him to toe the party line.

"I'm sure it's very difficult for him," said Tom Bracken, president of the New Jersey Chamber of Commerce.

Making it even more difficult is the fact that Frelinghuysen represents the Northeast in a party whose strength lies elsewhere.

"The Republican Party is dominated by southern and conservative interests," said Paul Herrnson, a political science professor at the University of Connecticut. "He doesn't fit that mold."

On his highest profile votes, Frelinghuysen switched his position and backed repealing the Affordable Care Act, which would have increased the number of uninsured in the state by 500,000, according to the progressive New Jersey Policy Perspective.

He also voted for a budget resolution that made it possible for congressional Republicans to pass a tax bill without any Democratic support. The bill gutted the state and local tax deduction used most often by residents of New Jersey and other high-tax states.

"He's dedicated to doing good for New Jersey, but, under these circumstances, he should have known better," said Rep. Bill Pascrell Jr., D-9th Dist., elected to Congress two years after Frelinghuysen.

"You either take the chairmanship or you say, 'Shove it,' and you do what you think is right," Pascrell said. "Rodney is never a person that I questioned his morality. I question his political good judgment though, this year particularly."

Trump himself weighs heavily on Frelinghuysen as well. Less than 40 percent of American approve of Trump's performance in office, according to opinion polls.

"If the 2018 election is a referendum on how voters feel about Republicans in Congress, the Frelinghuysens and his colleagues are in a very precarious situation," said Nathan Gonzales, editor of Inside Elections, another Washington-based publication that analyzes congressional contests.

Frelinghuysen is a member of a famous political family that predates the founding of the United States. His father once represented the district he now serves. There were Frelinghuysens in the U.S. Senate and on the 1844 Whig Party ticket as Henry Clay's vice-presidential nominee.

As Frelinghuysen runs for re-election next year, his leading Democratic opponent, former Navy pilot and federal prosecutor Mikie Sherrill, raised $744,014 through Sept. 30 and landed the backing of several progressive and Democratic fundraising groups such as VoteVets, Emily's List and End Citizens United.

"His stint as chairman of Appropriations has been breathtakingly bad for the citizens of New Jersey," Sherrill said of Frelinghuysen. "The numerous votes he's been taking shows very clearly where his priorities are. They certainly don't help the state."

When Frelinghuysen voted against his party leadership, he faced blowback from his fellow Republicans.

Take his vote against the original House Republican tax bill, which the progressive Institute on Taxation and Economic Policy said would raise taxes on residents of only four states, including New Jersey.

That led to calls from some House Republicans to strip Frelinghuysen of his chairmanship.

"They threatened his committee," said former Rep. Tom Davis, R-Va., elected the same year as Frelinghuysen, "They threatened him before his vote. He understood what the limits were. This would have a direct negative impact on a large part of his constituents. He saw that and he wanted no part of it."

Rep, Tom Cole, R-Okla., who sits on Frelinghuysen's Appropriations Committee, said lawmakers have to vote their districts.

"I don't know why he should be held to a standard that's different," Cole said. "No member gives up their voting card just because you have a position. If you think it's not good for the people you represent, your first obligation is to them."

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.