Gov. Andrew Cuomo and challenger Cynthia Nixon squared off in their first and probably only Democratic primary debate — a contest as fiery as the scorching weather outside Hofstra University, where the event took place.

Nixon fired the first shot, charging that Cuomo’s extensive experience wasn’t much of an asset unless he delivered.

“New York has the second most unequal education system when it comes to funding in the entire country. And I’m not an Albany insider like Gov. Cuomo. But I don’t think experience means all that much if you’re not all that good at governing,” she said.

When asked if he will serve all four years if re-elected, Cuomo says: “Yes and yes. Double yes.”

Asked the same question again, he added: “The only caveat is if God strikes me dead. Otherwise, I will serve four years as governor of New York.”

Pressed on the sorry state of mass transit in the Big Apple, Cuomo deflected and pointed the finger at the MTA and City Hall.

“You’re really referring to the New York City Transit, it is a shared city/state expense,” he said.

Nixon accused him of diverting cash from transit repairs elsewhere in the state budget.

“He used the MTA like an ATM,” she said as the tone deteriorated.

“Can you stop interrupting?” an irritated Cuomo snapped.

“Can you stop lying” she responded.

“As soon as you do,” the governor said.

Cuomo then went after Nixon for lobbying Mayor Bill de Blasio to stop helicopters from flying over the Public Theater’s performances of Shakespeare in the Park.

Nixon questioned the governor’s decision to deploy so many state troopers to Gotham, one of the key issues in the Cuomo-deBlasio feud.

Cuomo went after Nixon over the delayed release of her tax returns, which she revealed last Friday for just three hours.

“You have been as forthcoming on releasing your taxes as [President] Trump,” said Cuomo, who had criticized her for filing her taxes as a corporation rather than as an individual — a common practice for entertainers.

Nixon responded by calling the issue “a big nothingburger.”

“Maybe Donald Trump’s taxes are a nothingburger too!” Cuomo cracked.

Cuomo said he could support legalized sports betting.

“I support it in the right places under the right conditions,” he said, while Nixon said she wouldn’t support it without careful study.

Despite the acrimony, the pair shook hands as the hour-long debate wrapped up.

Earlier, the two-term governor’s campaign released a TV ad featuring old clips of Nixon heaping praise on the man she is running against

“God Bless Governor Cuomo,” Nixon said in one clip. In another, she said: “Governor Cuomo’s agenda, it’s incredibly progressive and it’s incredibly forward thinking.”

Nixon’s campaign countered that the undated videos came from 2011 and 2013 — long before Cuomo began feuding with de Blasio and other liberals from the Big Apple.

Nixon’s campaign quickly fired back.

“Cynthia has talked frequently during this race about how she voted for Cuomo in 2010 because she thought he would be a progressive like his father,” said Nixon spokeswoman Lauren Hitt.

“The fact that the governor broke his promises to so many progressives is a big part of why she is running.”

A day before, another spat broke out between the warring camps when a Nixon aide wanted to maintain the temperature in the debate hall at 76 degrees, far warmer than Cuomo likes it.

But while the debate was heated, the room was frigid.

Rebecca Katz, a strategist for Nixon, reportedly told WCBS — which sponsored the debate — that working conditions are “notoriously sexist when it comes to room temperature, so we just want to make sure we’re all on the same page here.”

A recent Sienna College poll found that Cuomo is ahead of Nixon, with a 60 to 29 percent lead, and he also has the financial edge, with $24.4 million on hand compared to Nixon’s $442,000. The primary is set for Sept. 13.