With less a month to go before the primaries, the three Democratic candidates for governor met for a debate Monday on Boston Herald Radio — and this debate made the others look tame.

At one point during the debate, the moderator marveled that during the commercial break, the candidates all got along.

Attorney General Martha Coakley confirmed it: “We’ve spent more time together than with our families so we do get along.”

But moments earlier, things weren’t so chummy. State Treasurer Steve Grossman attacked Coakley for going easy in a legal settlement with Beacon Hill lobbying firm The Brennan Group. The firm only had to pay back $100,000 out of $370,000 dollars in fees Coakley says were illegal. The lobbying firm had made political contributions to Coakley in the past, as Grossman pointed out.

“You know, I heard somebody the other day call this 'Lobbygate,'" Grossman said. "When it rises to the level of a 'gate,' I suggest it reflects on your judgement.”

Coakley said the settlement was appropriate. Then she hit back.

“I have always let people know who is giving money and who isn’t, unlike Super PACs that the treasurer has taken advantage of, or been benefited by, without knowing where the money was coming from,” she said.

Some top donors are known. Including Grossman’s 92-year-old mother Shirley, who donated $100,000. Grossman denied he was embarrassed by his mom, and invited the moderators to call her — going so far as to announce her phone number on air during the show.

The smiles wore off a few minutes later when candidate Don Berwick challenged Coakley to stand up to casinos and big money.

“It’s not the first place I would have gone for economic development," Coakley said before Berwick cut her off.

“Martha, it’s not economic development," Berwick said. "It’s economic decay.”

“No, I’m saying that’s not where I would have gone," she replied. "The legislature voted on it, Don.”

“So be a leader and say no," Berwick shot back.

Last week Charlie Baker, the leading Republican candidate, said if voters repeal the gambling law, and he becomes governor, he will file legislation to let Springfield still get a casino.

The Democrats were asked whether they’d do the same thing. Both Grossman and Berwick said no. Coakley said she’d consider it.