May 20, 2015 12:46 PM

Southampton Town Supervisor Anna Throne-Holst said on Tuesday afternoon that she will not seek reelection this fall—and instead will mount a challenge for U.S. Representative Lee Zeldin’s 1st District seat in the U.S. House of Representatives in the 2016 election.

Earlier this spring, Ms. Throne-Holst had said she was committed to continuing in her town role and was not looking forward to next year’s congressional race—even though she was seen as an immediate favorite for the challenger’s corner when Mr. Zeldin defeated six-term Democrat Tim Bishop. On Tuesday, she acknowledged that she had been approached about being a candidate for the federal post frequently in the past but had turned her sights to that prospect only very recently.

“I love my job as supervisor, and I so appreciate the people I work with and it’s a day-to-day relationship that I treasure,” she said on Tuesday afternoon. “On the other hand, I think my brand of ‘people not politics’ is sorely needed in Washington. I have a seven-and-a-half-year track record of minding the house and keeping a lid on taxes and cleaning up where cleaning up is needed. I think that’s the kind of legislating that is needed in Washington.”

Ms. Throne-Holst said the encouragement to challenge Rep. Zeldin has come from many corners of the Democratic Party, regionally and locally. She has not said when she will make an official announcement, though one is expected this week.

The three-term supervisor also said that once she came to the decision to seek the congressional seat, she decided it was not fair to Southampton Town residents to run for reelection to her town office in the interim. If she had won reelection to the supervisor’s office and had then won the congressional race, she would have had to leave town office with a year remaining on the term, leaving the town to hold a special election to fill its top post.

“I don’t want to mislead anyone—I’m not into smoke-and-mirrors, and I just didn’t think that was the right thing to do,” she said. “There’s a certain disingenuousness in that, and I wasn’t going to mislead my constituents and supporters.

“Instead, I will now focus all my attention for the next half a year on the business here—there’s a lot of work left to be done,” she said.

Ms. Throne-Holst is eligible to serve just one more two-year term as supervisor under town term limits law.

She was first elected to the Town Board in 2007, as a councilwoman, and then took over the supervisor’s office in 2009, defeating incumbent Republican Supervisor Linda Kabot. She won easy reelection to the post in 2011, when she was unchallenged, and again in 2013, in a rematch with Ms. Kabot.

During her tenure as supervisor, Ms. Throne-Holst oversaw steep cuts to town staffing levels, a broad reorganization of many of its government departments, and a rebuilding of financial accounts from deep deficits to robust reserves on the backs of stringent budget constraints. She has taken some lumps from groups of residents for her support of development projects like an apartment complex on Sandy Hollow Road and recently approved townhouses on the Shinnecock Canal.

Ms. Throne-Holst is expected to officially change her voter registration to Democrat before the election campaign gets rolling, as she would not be able to participate in a party primary otherwise.

She is currently registered with the Independence Party, which she helped establish as a political force in Southampton Town, but has been the Democratic Party’s candidate of choice in all four of her elections. When she first ran for office, she carried no political affiliation.

The supervisor is not the only person expected to seek to be East End Democrats’ choice to fight Mr. Zeldin next year. David Colone, a private equity manager and chairman of the Suffolk County Planning Commission, has already announced he plans to seek the Democratic nomination as well.

Mr. Zeldin’s press officer, Jennifer DiSiena, issued a statement Tuesday on behalf of the congressman in response to news of Ms. Throne-Holst’s expected candidacy.

“Congressman Zeldin has been working tirelessly in Congress since January, all day, every day, on important issues facing his constituents,” the statement read in part. “Congressman Zeldin will not be outworked, outclassed or out-gunned in pursuing victories for his district.”