OHIO — Tuesday’s fourth-round Democratic debate saw the dozen candidates throw as many punches at each other as at President Trump — with Elizabeth Warren vs. The Field serving as the main event.

The Massachusetts senator — still trailing front-running Joe Biden, but seemingly gaining ground on the former vice president with each new poll — found herself fending off attacks from mid-level candidates trying to drag her back to the pack.

The swipes came early, often and on several fronts at Otterbein University in Westerville, Ohio.

“The difference between a plan and a pipe dream is something that you can actually get done,” Minnesota Sen. Amy Klobuchar sniped at Warren and her Medicare-for-All program.

South Bend, Ind., Mayor Pete Buttigieg was game to tag-team Warren on health care.

“Your signature, senator, is to have a plan for everything. Except this,” said the normally less confrontational Buttigieg, riffing on Warren’s “I’ve got a plan for that” campaign slogan.

Former Texas Congressman Beto O’Rourke also got in a shot at the hard-charging Warren on the topic of the wealth tax she favors to help close the nation’s income-equality gap.

“Sometimes I think that Senator Warren is more focused on being punitive and pitting some part of the country against the other instead of lifting people up and making sure that this country comes together around those solutions,” said O’Rourke, referring to Warren’s well-worn rhetoric against billionaires.

Klobuchar — showing a previously untapped level of fire as she faces being frozen out of the next debate due to underwhelming poll returns — tagged back in.

“I want to give a reality check here to Elizabeth, because no one on this stage wants to protect billionaires. Not even the billionaire wants to protect billionaires,” she said, referring to outsider businessman Tom Steyer, making a largely invisible debate-stage debut.

The coordinated jabs seemed to stagger Warren.

“I’m really shocked at the notion that anyone thinks I’m punitive,” she replied, appearing genuinely taken aback. “I don’t have a beef with billionaires.”

As many focused on Warren in their cross hairs, one candidate took the opportunity to slip into the shadows for much of the contest: Joe Biden.

Biden kept a low profile until the debate’s third act, when he found himself pitted against Warren and Vermont Sen. Bernie Sanders — together the three most-tenured candidates in the race — on their records of cutting through Beltway red tape.

“I went on the floor and got you votes!” to form the Consumer Financial Protection Bureau, thundered Biden at Warren, who originally championed the watchdog group’s creation in 2007.

“You did a hell of a job at your job,” he added.

After a tense pause, Warren replied with a simple, “Thank you.”

On a night marked by Democrat-on-Democrat infighting, it was the often cantankerous Sanders who provided sparks of levity and unity.

“Let me take this moment, if I might, to thank so many people from all over this country, including many of my colleagues up here, for their love, for their prayers, for their well wishes,” said Sanders, 78, back on a national stage two weeks to the day after suffering a heart attack on the campaign trail in Nevada.

Sanders received a warm ovation from both the audience and his fellow competitors, and showed no ill effects from the health scare, firing on all of his characteristically cranky and kooky cylinders.

“I’m healthy, I’m feeling great,” said Sanders, before he was cut off by a crack from New Jersey Sen. Cory Booker about Sanders’ support for marijuana ­legalization.

“I’m not on it tonight,” said Sanders, shooting back a smile.

Sanders also hammed it up when Biden wrapped an arm around his shoulder to use him as a prop when talking about Trump’s relationship with Russian President Vladimir Putin.

“You’re suggesting I’m Vladimir Putin here?” asked Sanders, drawing a chuckle from the crowd — and Biden.

Candidates like California Sen. Kamala Harris, Hawaii Rep. Tulsi Gabbard and former Housing and Urban Development Secretary Julián Castro had more anonymous nights.

It’s a luxury Harris can weather, but that may prove damning for Gabbard and Castro, on the bubble for next month’s fifth-round debate.

What remains of the field will meet again on Nov. 20 in Georgia.

Additional reporting by Julia Marsh