WASHINGTON — Democrat Rep. Chris Pappas bested Republican John Sununu Tuesday to become America’s first-ever openly gay male senator and keep the party’s winning streak going in the Granite State.

Pappas, 46, had been favored to win the race to succeed retiring three-term Sen. Jeanne Shaheen (D-NH), but tighter-than-expected polling over the summer and into early fall prompted national Democrats to pump more cash into the race.

Sununu, 62, had been the most recent Republican to hold the seat following his defeat of Shaheen, then the state’s governor, in 2002 — only for her to get her revenge in a rematch six years later.

The son of one popular Republican governor and the brother of another, the GOP nominee was accused by Pappas of trying to trick voters into thinking they were backing Sununu’s younger sibling, Chris, by distributing yard signs reading “Sununu Senator.”

“Look, if people thought they were voting for me, my brother would be up by 30 points. Come on,” Chris Sununu quipped to CNN when asked about the dynamic last week.

Despite his popular family name, Sununu faced significant national headwinds due to affordability concerns, President Trump’s sagging approval rating, the high cost of gas, and unease about the conflict in Iran.

In one of his closing campaign ads, Sununu stressed that despite Pappas attempting to portray him as President Trump’s “long-lost son,” the Republican said he had “never even met the man” and stood by an op-ed he once wrote describing Trump as a “loser.”

While Republicans have dominated the New Hampshire legislature and governorship over the past decade, they’ve struggled to break through in federal races. The Granite State hasn’t voted for a GOP presidential candidate since 2000, hasn’t elected a Republican to the Senate since 2010 and last returned a GOP congressman in 2014.

Pappas, a Harvard-educated descendant of Greek immigrants, is part-owner of the popular Puritan Backroom restaurant in Manchester, which claims to have invented the chicken tender.

While the Democrat campaigned with prominent figures like former Vice President Kamala Harris and California Gov. Gavin Newsom, Sununu focused on retail politicking — barely even campaigning with his brother.

“There’s really no need to campaign with anyone else,” he explained to The Post. “In New Hampshire, they want to meet the candidate. You go town to town, person to person.”