Debra Messing has been a Democratic darling for decades — campaigning for Hillary Clinton, donating to Cynthia Nixon’s run for governor, standing as one of Donald Trump’s fiercest Hollywood critics.

And last week, she endorsed Republican Bruce Blakeman in his bid to unseat Gov. Kathy Hochul.

Why? Practical reasons: climbing utility bills, tolls to drive into Manhattan and neighbors giving up and leaving due to Hochul’s mismanagement.

And as an outspoken supporter of Israel who’s called Mayor Zohran Mamdani an “American-hating jihadist,” Messing has plenty of reasons for discontent with a governor who kowtows to him.

“I was born here. This is the city I love,” Messing told Blakeman. “And it’s not the city that I love anymore.”

There are a lot of Debra Messings out there: lifelong Democrats and former progressives who look at the party with disbelief and growing alienation.

I know — because I am one.

That means there’s a golden opportunity to build a DSA-busting coalition of Republicans, up-for-grabs independents and disillusioned Democrats here in New York.

It’s the only path back to the sensible center — where the people who pay the taxes, build the businesses, buy the homes and raise the children of this city actually live.

Last year I crossed over to run on the Republican line against uber-progressive Manhattan DA Alvin Bragg, to combat the crime-coddling policies that have made our city unsafe.

“You’re the first Republican I ever voted for,” countless Manhattanites told me — and I got 100,000 votes, more than half of them from Democrats or independents.

It wasn’t enough to win, but it proved that plenty of registered Democrats are fed up enough with far-left policies to vote for a Republican, even in the era of Donald Trump.

And this year, Blakeman isn’t the only local Republican drawing interest from across the aisle.

Caroline Shinkle, an outstanding GOP congressional candidate for NY-12 in Manhattan, was just endorsed by hedge funder Bill Ackman, a longtime Democrat donor.

Saritha Komatireddy, a former federal prosecutor and DEA chief of staff running for attorney general, has also been gaining in the polls — and on Thursday night she demolished Letitia James in their first debate with an impressive display of competence.

Komatireddy slammed James for the “nosedive” in Medicaid fraud recoveries on her watch, her failure to act on patient-abuse complaints and her refusal to act against rising antisemitic hate crimes.

She deftly defanged James’ attempt to attack her on abortion by sharing about her own high-risk pregnancies.

Unlike James, Komatireddy could instantly name a past AG she admired — and when asked about the last book she’d read, she charmingly answered “Little Blue Truck,” her toddlers’ favorite.

Blakeman, Shinkle and Komatireddy are all offering a commonsense approach to governance that appeals to the vast middle.

But to actually win, they need field operatives with the local knowledge and know-how to get out the vote — something that has all but vanished among NYC Republicans.

The DSA has a multi-decade head start.

And money: The Commie Corridor does not come cheap.

Salaried leaders, pricey new offices and a social-media machine that now runs partly out of City Hall on our dime fuel their wins.

But the Coalition of the Sane — Republicans, independents and disaffected Democrats — can catch up fast if we do three things.

First, we need to convince New Yorkers that the Democratic primary isn’t the only game in town.

Republicans need to make coalition-building their watchword, and that means running strong candidates in each and every general election — refusing to let Dems run unopposed.

We need to invest in organizations that recruit, train and fund a new generation of Republican candidates and campaign staff — groups that talk to communities year-round, just like the DSA does.

We need to register more independents and Republicans, and launch a campaign to get disaffected Democrats to leave the party.

Unaffiliated voters are already the fastest-growing bloc in New York — and every voter who leaves the Democratic ranks is a loud signal that the primary no longer needs to decide every election.

Some New York Democrats are so tangled in Trump hatred that they’ll never vote for anyone associated with him.

But Messing is proof that such distaste is not an insurmountable obstruction.

She’s crossing over anyway, because the election in front of her is about her city, not about Washington.

And that’s showing how Republicans can compete in NYC: by building a local brand focused on local issues — affordability, public safety, quality of life, good schools and competent government.

It seems like a challenge of biblical proportions, a David-and-Goliath fight, to form a coalition of New York City voters ready to vote for a Republican.

But like taking a slingshot into battle with a giant, that’s how game-changing victories are won.

Maud Maron is a New York attorney and education advocate.