The next congressional election may be 15 months away, but contenders for the Democratic nomination in the 1st District already are visiting Washington, raising money and huddling with local party leaders as they look to oust Republican Rep. Lee Zeldin next year.

“Unfortunately, this is the not the age when Otis Pike could decide in February or March what he was going to do in the next election,” said Assemb. Fred Thiele (I-Sag Harbor), referring to the Democrat who served from 1961 to 1979 in a district that has swung between parties five times since.

Thiele, 63, a 22-year state lawmaker, former Suffolk County legislator and Southampton Town supervisor, is the most veteran official eyeing the congressional race.

Term-limited Suffolk Legis. Kate Browning, 57, who like Zeldin is from Shirley, is weighing a run, and backers say she could cut into Zeldin’s hometown base.

Both say they plan to make a decision by around Labor Day — this year.

Former county lawmaker Vivian Viloria-Fisher, 69, a Setauket Democrat, already has declared her candidacy and has raised $35,619 for the race.

Perry Gershon, a businessman who moved his voting address from Manhattan to East Hampton last month, has formed a fundraising committee. He said in his first two weeks he has raised $180,000, although he has yet to file a fundraising report with the Federal Election Commission.

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Brookhaven National Laboratory scientist Elaine DiMasi also is considering a run, but is covered by the federal Hatch Act and would have to leave her job to do so.

Richard Schaffer, Suffolk Democratic chairman, said Zeldin is vulnerable “because he is lockstep with the disastrous Republican agenda to take away health care from millions of people and do permanent damage to Long Island’s environment and its struggling middle class.”

Emily’s List, a political action committee that backs Democratic women who support abortion rights, has put Zeldin among its top 50 targets.

John Jay LaValle, Suffolk Republican chairman, dismissed Democrats’ chances to beat Zeldin.

“They are setting themselves up for a race to see who can lose to Lee Zeldin,” LaValle said. He described Zeldin as a “tireless worker, who knows how to make a difference in Washington and deliver resources to his district.”

LaValle said Zeldin has brought home funding for Brookhaven Lab, East End environmental issues and supported the U.S. military. “He’s sitting at the table with the highest levels. The president literally called him several weeks ago to have dinner with him,” LaValle said.

Thiele and Browning say it is critical that Democrats avoid a costly primary next year. They cited the First District Democratic primary last year — after which winner Anna Throne-Holst lost by a margin of 16.4 percentage points to Zeldin.

Viloria-Fisher said she would prefer to avoid a primary, “but I can’t see leaving this race.” Even Gershon, who is little known but appears to have substantial funding, could force a primary.

The front-runners, however, have their issues.

Thiele and Browning may sit with Democratic majorities, but have belonged to minor parties — Thiele, the Independence Party, and Browning, until recently the Working Families Party. She has re-enrolled as a Democrat, but the change does not take effect until after Election Day this year.

And Viloria-Fisher, after leaving the county legislature in 2011 due to term limits, lost her last race — a run for supervisor of Brookhaven Town in 2013, which makes up two thirds of the congressional district. Incumbent Republican Edward Romaine beat her by 62 percent to 38 percent.

Schaffer says he aims to pick a candidate by early fall without an intraparty fight. He said he is banking on the things the candidates and potential candidates have in common.

“All the people in this race have common sense,” he said. “And they have a common goal to defeat Zeldin.”