Former Nassau County Executive Thomas Suozzi defeated a pack of four other Democrats vying to replace Rep. Steve Israel in a primary for New York’s 3rd Congressional District on Tuesday night.

Meanwhile, former Southampton Town Supervisor Anna Throne-Holst and venture capitalist David Calone were locked in a tight race in the Democratic primary for the 1st Congressional District. Throne-Holst led by 29 votes with more than 1,600 absentee ballots still to be counted.

Suozzi’s margin of victory came in Nassau County and Queens. The district also includes portions of northern Suffolk County.

“We’re going to win this election, we’re going to win on the issues,” Suozzi told a crowd of more than 200 supporters gathered at Ben’s Kosher Deli in Greenvale for an election night party.

Suffolk County Legis. Steve Stern, 47, of Dix Hills, the lone candidate from Suffolk in the field, entered the race with Israel’s endorsement and led in his home county, but came in second overall.

Shortly after 11 p.m. Stern conceded the race to Suozzi.

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“I will strongly support the Democratic nominee to ensure this district remains a Democratic seat,” Stern said.

Suozzi, 53, of Glen Cove was one of four Nassau contenders competing for the seat, including former North Hempstead Supervisor Jon Kaiman, 53, of Great Neck and North Hempstead Town Councilwoman Anna Kaplan, 49, of Great Neck, who all ran touting their government experience. Attorney Jonathan Clarke, 39, of Jericho ran as an “outsider” aligned with the values of Democratic presidential hopeful Bernie Sanders.

Suozzi thanked all his opponents for “running a positive campaign” and said he was running in the hopes of changing the “culture” of partisan gridlock in Congress.

All five were vying to run against state Sen. Jack Martins (R-Old Westbury) in the November general election in a district in which Nassau composes 50 percent of the registered voters, compared with 30 percent in Suffolk and 20 percent in Queens.

Calone and Throne-Holst waged this year’s most expensive Long Island primary, according to campaign finance records showing each spent $1 million on their primary battle.

The spending underscored the importance of the swing district to Democrats and Republicans nationally, as House Democrats look to reclaim the seat they lost to Rep. Lee Zeldin in 2014.

Calone called the race a “tie,” telling supporters shortly before 11 p.m. that absentee ballots would decide the race.

“This story does not end tonight,” he said, adding that counting the absentee ballots would begin next week.

At 11:15 p.m., Throne-Holst addressed a room full of supporters, thanking them for support.

“This night went a little bit later than we thought, but we’re leading by a hair-thin margin,” she said. “We’ll count the absentee ballots and usually, absentee ballots mirror those at the polls. I’m confident that will happen again.”

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Calone, 42, of Setauket and Throne-Holst, 56, of Sag Harbor traded attacks throughout the primary race.

Calone released an ad that tried to tie his rival to presumptive Republican presidential nominee Donald Trump through small donations she gave to a local Conservative party.

Throne-Holst criticized Calone’s tenure on the Long Island Power Authority board of trustees from 2009 to 2012 for rate hikes implemented during that period.

Meanwhile, nine-term Rep. Gregory Meeks of St. Albans, Queens, soundly defeated Ali Mirza, 58, an Elmont businessman in the 5th Congressional District Democratic primary, according to poll results.

The 5th District is largely based in Queens but contains a slice of western Nassau.

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With Rick Brand, Robert Brodsky, Scott Eidler, Will James and David M. Schwartz