Still, there were occasional flashes of conflict which showed the candidates aren’t as similar as they might seem — and hinted at how the race might unfold between now and the April 30 primary.

The sharpest exchange came, unexpectedly, on the issue of prosecutorial conduct. Asked to weigh in on Senator Elizabeth Warren’s call to criminally prosecute banks that behave badly, Sullivan replied that while such prosecutions may sound appealing, they risk harming employees and shareholders.

Winslow — who’s a former judge — pounced, decrying what he called excessive prosecutorial discretion to either not prosecute or pursue cases with extreme aggression. As an example of the latter, Winslow cited the recent federal case against Aaron Swartz — the open-internet activist who was accused of illegally downloading millions of articles via MIT’s network and recently committed suicide. That case, it’s worth noting, was pursued by Carmen Ortiz, Sullivan’s successor as U.S. Attorney.

Immigration was another point of disagreement. Gomez, whose parents immigrated from Columbia, touted the prospects for a bipartisan “pathway to citizenship,” but said he’s utterly opposed to amnesty. For his part, Sullivan backed amnesty for illegal immigrants who’ve served in the armed forces. (“If they’ve attempted to make our national security and nation strong, put themselves in harm’s way, I think they deserve amnesty,” he said.) But Winslow was uncompromising.  “I don’t agree with amnesty,” he said bluntly. “... We have to make the front door [of immigration] work better. We have to close the back door."

The candidates also sparred on the question of comportment, a topic that put Winslow on the hot seat. WCVB’s Janet Wu observed that Winslow is known for his flamboyant approach to politics — among other things, he’s hosted a “beer pong” fundraiser and delivered jars of Marshmallow Fluff to Governor Deval Patrick to make a point about the state budget — and asked if that sort of behavior could be described as senatorial.

Winslow defended his approach. “I’m in the loyal opposition; my role is to poke back against and to speak truth to power in the state government,” he argued. “And I intend to do the same thing down in Washington, because people have to ask the questions, and people have to take the stands, and sometimes it’s good to make a point.”

Sullivan and Gomez, however, were unimpressed. “I don’t need to grandstand and do things like that,” Gomez jibed. “I just cannot see myself participating in that kind of theatrics,” Sullivan added, “unless it was for the sole purpose of trying to be humorous.”

Another lesson from Tuesday’s proceedings: the three candidates have remarkably different styles at this point in the campaign. Gomez, who’s never run for office before, is the greenest of the bunch, and he looked and sounded the part. His hands appeared to shake nervously for much of the evening, and referenced his go-to concept — that he's not a career politician — a bit too frequently. Sullivan, for his part, seemed calm and supremely confident throughout, while Winslow was the highest-energy candidate of the bunch. (After Gomez and Sullivan delivered their closing remarks from the comfy chairs provided by Stonehill, Winslow sprang to his feet to give his parting comments.)

One more thing: keep an eye on the abortion issue as the GOP primary fight continues. When I asked Sullivan about the merits of Roe v. Wade during the forum, he made it clear that he believes that decision was bad law. After the forum, meanwhile, Winslow noted that he’s the only pro-choice candidate in the race — and said that overturning Roe v. Wade would require the rejection of years of legal precedent. Yet during the forum itself, Winslow, like Sullivan, rejected the idea that they might oppose a Supreme Court nominee who thinks Roe v. Wade should be overturned. Depending on how he finesses it, Winslow’s stance on abortion could be an asset in a general election — and a major liability in a GOP primary. As of now, he still seems to be figuring out the right way to proceed.