LOWELL -- Moments after state Attorney General Thomas F. Reilly urged his fellow Democrats to broaden their appeal beyond their liberal base, delegates to Massachusetts Democratic Party yesterday voted overwhelmingly to endorse gay marriage in their platform.
Reilly, one of three likely gubernatorial candidates to address the convention, told the crowd of more than 2,500 delegates that it was crucial to win back moderate suburban voters who have helped elect Republican governors over the last 15 years.
''We have to convince ordinary people that we understand what's going on in their lives," Reilly said, ''and that we can help make their lives better."
Reilly did not mention gay marriage in his speech and refused in an interview afterward to say whether he supported the platform change. He has said recently that he now supports gay marriage, after he indicated last year that he preferred permitting gay and lesbian couples to join in civil unions rather than full-fledged marriage.
The convention gave dyed-in-the-wool Democrats their first chance to size up the party's three gubernatorial candidates: Reilly, former US assistant attorney general Deval Patrick, and Secretary of State William F. Galvin, who has yet to make a formal announcement of his candidacy.
Patrick struck a number of ideological themes that energized the liberal core that dominates Democratic convention crowds. He declared his support for gay marriage and decried Republican Governor Mitt Romney's call for an income tax rollback and the governor's campaign to bring back the death penalty. The speech was interrupted several times by applause and ended in a standing ovation.
''When somebody tells you we can't win back the corner office with a candidate who hasn't paid his political dues and stored up his political chits on Beacon Hill, what are you going to say?" Patrick said. The crowd roared back, ''Yes, we can!"
Galvin said he would be a governor who works solely for Massachusetts and not to achieve higher office -- a shot at Romney and his Republican predecessors William F. Weld and Paul Cellucci, who both used the corner office as a springboard for federal posts.
''After 20 years of neglect by a succession of dilettante Republican governors," Galvin said, ''we're witnessing nothing less than the crushing of Massachusetts."
Tim O'Brien, executive director of the state Republican Party, dismissed the criticism.
''It was liberal candidates talking about their left-wing agenda to a group of people that don't represent the average voters of Massachusetts," O'Brien said in a telephone interview.
The gay-marriage plank was approved as part of a voice vote that also approved the party's entire platform. The vote, which capped the Democrats' convention at the Paul E. Tsongas Arena in Lowell, left the Bay State Democratic Party the third in the nation to back same-sex marriage, staking out an ideological position that puts it in contrast with most of the nation and the platform of the Democratic National Committee.
There was a smattering of no votes in the crowd of delegates, but no one spoke out against the platform change. A total of 2,538 delegates were registered at the convention.
The addition to the Democratic Party's platform reads: ''We affirm our commitment to the Massachusetts constitutional guarantee to same-sex marriage, and all of its rights, privileges, and obligations, and reject any attempt to weaken or revoke those rights."
Previously, the platform endorsed civil unions.
For the most part yesterday, the partisan rhetoric was fairly tame. US Senator Edward M. Kennedy, who is up for reelection next year, chided President Bush for being out on his mountain bike while an errant Cessna aircraft forced the evacuation of Congress and most of official Washington.
Instead of focusing on the gay-marriage plank, most eyes were trained on the three seeking the governorship. One will try to give the Democrats their first win in a governor's race since 1986, when Michael S. Dukakis won a landslide victory over GOP candidate George Kariotis.
In recent months, Romney's popularity has waned in the state, as he has tested the presidential waters by traveling out of state and stepping up his conservative rhetoric. A poll conducted late last month by the University of Massachusetts at Lowell indicated that 33 percent of those surveyed thought Romney deserved to be reelected, a 10-point slide from a poll on the same question in January. Other polls have indicated Reilly holding an advantage over Romney in a hypothetical head-to-head contest as well.
Still, Romney's victory in 2002 over Democrat Shannon O'Brien was due in large part to his popularity among independent voters in the vast suburban ring around Boston.
For Reilly, his speech was in many respects a triumph compared with the 2003 convention, when he was booed by the party faithful.
Patrick, who remains a virtual unknown to many Bay State voters, appeared to instantly connect with the delegates.
But Patrick said he agreed with Reilly that the party must broaden its appeal if it is to win back the corner office, and he agreed with the national party chairman, Howard Dean, that the gubernatorial candidates must conduct a civil campaign that leaves the ultimate winner in a strong position to beat the Republican nominee.
Interviews with some of the few undecided Democrats in the arena yesterday indicated that Reilly, Patrick, Galvin, and other potential candidates such as US Representative Michael E. Capuano of Somerville have a long way to go before they can count on their party's nomination.