Trailing heavily in polls with only 24 hours to go before the primary, state Sen. Michael J. Barrett '70 (D-Cambridge) charged in a debate this weekend that his challengers have consistently pandered to special interests.

During Friday afternoon's taping of Channel 56's "Let's Talk Politics," which aired last night, Barrett questioned the integrity of his Democratic opponents--state Rep. Mark Roosevelt '78 (D-Beacon Hill) and former state Sen. George Bachrach (D-Watertown).

While all three Democratic candidates have criticized Gov. William f. Weld '66 for catering to his wealthy contributors, Barrett asked why both Bachrach and Roosevelt have accepted contributions from political action committees (PACs).

"How can we deal with our own potential ethics violations?" Barrett asked, unfurling a two-foot-long white scroll detailing approximately $30,000 in PAC contributions to the Roosevelt campaign.

Roosevelt asserted that his acceptance of PAC money did not constitute an ethical violation because it came primarily form labor unions, not organizations representing wealthy people.

"I'm happy to accept their dollars," Roosevelt said. "That is how these people can participate in politics."

Bachrach, in response to Barrett's accusation, said that perhaps Barrett has no accepted PAC money because nobody has offered him any.

"I'm not aware of a single group that has endorsed you," Bachrach said to Barrett.

But the Cambridge state senator responded that he has turned down contributions from organizations.

"It created the impression of a conflict of interest," he said.

After the debate Bachrach said Barrett may have attacked him and Roosevelt out of desperation.

"Mike has been consistently in third place," Bachrach said. "Negative campaigning is the last resort. It may hurt the person lobbing the hand grenades."

During the rest of the debate, the candidates reiterated the themes central to their campaigns.

All candidates characterized Weld as aloof and uncaring, while admitting that the administration of former Gov. Michael S. Dukakis had several faults, particularly in fiscal management.

Bachrach, as expected, described himself as a "progressive Democrat" despite the fact that "a frustrated public" currently wants Democratic leaders "to be more like the Republicans."