The three Republicans vying for Massachusetts’ open Senate seat debated gun control regulations at the WBZ-TV studios in Allston Wednesday night, hours after news outlets reported a bipartisan Senate compromise on the issue.

State Representative Daniel B. Winslow and former U.S. Navy SEAL Gabriel E. Gomez, said they would support the compromise—which proposes the extension of background checks to firearms purchased at gun shows. But former U.S. Attorney Michael J. Sullivan, who served as the director of the Bureau of Alcohol, Tobacco, Firearms, and Explosives, struggled to make the same commitment, even when pressed by his fellow Republicans.

“The issue is whether or not [the compromise] really solves the problem [which is] keeping guns out of the hands of criminals and...the adjudicated mentally ill,” Sullivan said. “And it doesn’t.”

When Winslow interjected to ask if Sullivan would clarify his vote—yes or no—Sullivan countered with a question, prompting a parlay of hypothetical questions between the two men until Winslow demanded a direct answer for the sixth time.

“You’re in the United States Senate: how would you vote on the compromise?” he asked.

Sullivan did not change his tack.

“It doesn’t address the problem,” Sullivan said. “I’m not going to do something just because it feels good.”

The debate covered a number of other issues, including President Barack Obama’s budget proposal—which all three candidates said they oppose—as well as entitlement reform and immigration.

Gomez and Sullivan tussled briefly on the issue of a path to citizenship for illegal immigrants, a policy that Gomez has supported in varying forms and one against which Sullivan has cautioned.

Still, the exchange over gun control was the story of the night. Gomez, who has campaigned on his status as a political newcomer, told the media afterward that the gun regulation discussion was especially revealing.

“I think what you saw today was one person who has never been in politics... and two other people who have been in politics since the 1990’s, bickering back and forth and giving a very clear example of what is going on down in D.C.,” he said. “I was psyched to be out here. It shows exactly...why I stand out among the other two.”

“They proved my point today,” he added. “I couldn’t be happier.”

Winslow appeared just as confident.

“I’ve been to a lot of debates,” he told reporters. “I’ve never seen somebody duck a question the way Mike Sullivan did today.”

Sullivan remained consistent in his post-debate media session. Asked about his vote on the gun law, his first words aptly summarized his position.

“I don’t know,” he said.

—Staff writer Matthew Q. Clarida can be reached at clarida@college.harvard.edu. Follow her on Twitter @MattClarida.