Sen. Kirsten Gillibrand is already fundraising off the threat of a Lee Zeldin 2024 challenge — even though the Republican former congressman, who nearly toppled Gov. Kathy Hochul in November, remains non-committal about campaigning for another DC job.

“Our potential Republican opponent, Lee Zeldin, just attacked Kirsten Gillibrand on Twitter. As we gear up for the tough reelection fight ahead, we know this is only the beginning,” reads the email plea.

“Zeldin very nearly won the New York governorship in the 2022 midterms, all, while New York Republicans had their best election cycle in two decades — flipping enough House, seats red to retake the majority,” reads a fundraising pitch sent Wednesday to supporters.

The message came one day after Gillibrand told a local news station, “I will beat him,” if the Long Islander does decide to run to become the first Republican senator from New York since Alphonse D’Amato left office in 1999.

Zeldin on Friday responded to her comments with mockery.

“Tough talk from New York’s laziest and most forgettable Senator in generations. Senator What’s Her Name only says this because she is in a state with MANY millions more Dems than Republicans. If the Dem enrollment advantage was 2 million, that wouldn’t be enough. She’d be toast,” he tweeted.

Whether or not Zeldin runs, Gillibrand stands to gain a lot by fundraising early given the possibility of a competitive Democratic primary next year against the likes of progressive superstar Rep. Alexandria Ocasio-Cortez (D-Bronx).

Recent filings show AOC has roughly $5.4 million in her campaign account compared to $4 million for Gillibrand.

Both of them might need millions to beat Zeldin considering his performance in the November gubernatorial race.

Republicans managed to flip the U.S. House in 2022 in part because Zeldin – who lost to Hochul by a 53%-47% margin – helped drive turnout while coming closer to winning statewide office than any other Republican over the past two decades.

“I think he would run, that certainly a brass ring seat for Republicans, and he’s not got a proven track record running well statewide and raising enough money to compete,” GOP political consultant Chapin Fay, who has worked for Zeldin in the past, told The Post.

“Not sure any other Republican would be as strong a candidate as he would,” Chapin added.

His Long Island roots might position him well against an upstater like Gillibrand too.

“Based on how well he did last November, Zeldin would no doubt run strongly on Long Island, and have a chance at blunting Gillibrand‘s appeal upstate,” Larry Levy, executive director

But Zeldin would face big hurdles in a race against Gillibrand if he challenged her bid to be elected for a third term after she was appointed in 2009 to replace Hillary Clinton when the former first lady was tapped to be secretary of state under President Barack Obama.

Registered Democrats outnumber registered Republicans statewide, which disadvantages any GOP candidate in a statewide race.

Gillibrand has also notched some legislative wins in recent years after dropping out of the 2020 Democratic primary for president that might energize the party base, including leading efforts to better address the plague of sexual assaults in the military by shifting such cases away from the chains of commands within the uniformed services.

And then there is the likelihood that voters will turn out in much bigger numbers in a presidential election year compared to the 2022 gubernatorial election where relatively high GOP turnout helped Zeldin against Hochul.

“He could run, and would probably be the strongest Republican candidate, but he won’t win,” Democratic consultant Evan Stavisky said.

“Presidential and midterm elections are like apples and oranges. More than 2.5 million more people turned out to vote in the 2020 Presidential Election in New York than in last year’s race for Governor.  Joe Biden alone got nearly as many votes in 2020 as the Governor and Zeldin got on their major party lines combined last year,” he added.

The former four-term congressman has not ruled out a 2024 Senate run while keeping his options open after declining to run for chair of the Republican National Committee.

“I have received calls asking me to consider running for Senate, Suffolk County executive, [speaker of] the House of Representatives, NY GOP chair, RNC chair and more. I am very grateful to everyone for their passionate outreach, but I don’t have any updates to announce at this time,” he told The Post.

Whether or not Zeldin does run, Gillibrand is expressing confidence about her chances of beating the eventual GOP Senate nominee while leveraging the Suffolk pol in the meantime to raise money for her reelection campaign – and a potential match-up against progressive superstar Rep. Alexandria Ocasio-Cortez (D-Bronx).

“Lee Zeldin all but admitted in his rage tweet that he can’t beat Senator Gillibrand. Senator Gillibrand won her first election by unseating a powerful incumbent in a two-to-one Republican district and went on to win reelection with 62% of the vote while also being pregnant and giving birth that Congress,” Gillibrand spokesman Evan Lukaske said Friday.

“She has since gone on to beat Republican opponents by historic margins and is confident she’ll beat any Republican opponent…handily,” he added.