Candidates spar -- gently -- in Senate debate

But Pagliuca, a co-owner of the Boston Celtics, and Khazei, a co-founder of City Year, tried to define themselves as Beltway outsiders who were free from special interests and would arrive in Washington with fresh eyes.

‘‘I know it is rocket science down there to get things done,’’ Pagliuca, his voice dripping with sarcasm, said at one point when Capuano suggested he was the only one who understood Washington.

Khazei, arguably the least-known candidate in the field, attempted to stand out by saying that he would not take any donations from lobbyists and political action committees.

‘‘We need to end the dominance of the PACs and special interests,’’ he said. ‘‘There’s an old Italian saying, ‘You can’t get clean water until you get the hogs out of the creek.’’’

‘‘Alan’s not taking that money,’’ Pagliuca added. ‘‘I’m not taking that money.’’

But Capuano and Coakley are taking that money, and the exchanges last night suggested that distinction could loom large in a Democratic primary in which the candidates share many policy positions.

The debate, held at the John F. Kennedy Presidential Library and Museum, was broadcast live on nearly every Boston-area television network and several radio stations. It was revealing at times, but there was little friction and virtually none of the sharp exchanges that often animate such clashes.

Though a few policy differences emerged, the four largely agreed on the major issues, from whether to send more troops to Afghanistan and how to get to universal health care, to immigration and economic issues. They all largely leaned left in their positions and comments as they appealed to the liberal base of the Democratic Party, which dominates the primary electorate.

The format generally limited back-and-forth among the candidates, with moderator Peter Meade, the chief executive of the Edward M. Kennedy Institute, asking all the questions and guiding the debate. None of the candidates had any experience on such a large stage, and it was an event all candidates have spent weeks preparing for.

With Coakley well ahead in the polls six weeks before the Dec. 8 Democratic primary, it was the best opportunity yet for her three competitors to change the dynamic. Coakley made no major missteps, although she also did little to demonstrate any sharp differences she has with her opponents, in style or on the issues.

‘‘I believe I’ll be a new leader, a new kind of leader in Washington,’’ Coakley said.

Capuano began the debate by highlighting his blue-collar roots in Somerville. The six-term congressman, who graduated from Dartmouth College, said part of his motivation for running was to prove that ‘‘working-class people’’ could excel in the United States.

‘‘If somebody like me doesn’t step up and try, then somebody like me will never be able to succeed in this country,’’ he said.

The economy dominated several portions of the debate, whether it was discussion of whether they would support another round of federal stimulus funding — all said more or less that they would — or whether they could bring more jobs to Massachusetts.

‘‘People are hurting. You’ve lost your jobs, your homes, your retirement, your children’s dreams of a college education,’’ Khazei said. ‘‘Washington is stuck when we need action.’’

One of the only notable disagreements came over health care, with Capuano striking a more liberal stance than his opponents. Informing the debate was a proposal outlined yesterday by Senate Majority Leader Harry Reid that called for a government insurance option but also a provision allowing states to decline that option.

Capuano said he would be unlikely to support a plan that would allow states to opt out of coverage. He also said Republican support wasn’t necessary.

‘‘When you have the votes, you go for it,’’ playing down the importance of broad consensus. ‘‘They didn’t wait for it on WPA. They didn’t wait for it on Social Security. They didn’t wait for it on Medicare. We shouldn’t wait for this to make sure that everybody’s happy, because we’ll never make everybody happy.’’

Coakley countered that an approach like Reid’s might work, and that getting some reform in place should be a priority.

‘‘We’re desperate to make some progress on this,’’ she said. ‘‘At this stage, we need movement and we need to make some reforms.’’

Capuano refused to answer specific questions on immigration. Asked whether he would vote to provide illegal immigrants with health care or driver’s licenses, he said, ‘‘Those are false choices. Those are the divisive issues.’’

When Meade pressed, Capuano said, ‘‘We wouldn’t have to have that vote, Peter. It wouldn’t come up.’’

The three other candidates said they supported a broad immigration overhaul that would provide a path to citizenship, but they did not necessarily support issuing driver’s licenses or providing health care for those here illegally.

Capuano, boasting about how he has helped bring billions into the state in federal spending — for health care research, education funding, and fresh revenue for local communities, cast himself as the ultimate Washington insider who can make the system work for Massachusetts.

‘‘That is part of being a senator that can only be done if you know how to work in Washington,’’ he said. ‘‘If you think you can do down and change Washington like this, God bless you — good luck.’’

‘‘I may be naive, but I think we can change Washington, and I think we need to change Washington,’’ Paglicua retorted.

Kennedy’s name came up throughout the debate, whether it was his method for hiring staffers or his horse-trading to make a deal.

‘‘It obviously carries with it great weight,’’ Coakley said of running for his seat.

‘‘Senator Kennedy would have wanted me to do this,’’ Pagliuca said. ‘‘I’m running with the passion of Senator Kennedy in my mind every day.’’

The winner of the primary will face off against a Republican opponent in a Jan. 19 special election; the leading GOP candidate is state Senator Scott Brown of Wrentham.

Earlier in the day, Khazei, in a surprise move, came out against legislation on Beacon Hill to license casino gambling, saying the industry thrives by preying on low-income residents.

‘‘Casino gambling will irrevocably change the culture and fabric of our state. It’s a decision we can’t change,’’ Khazei said at the forum, which was sponsored by the casino-friendly Greater Boston Chamber of Commerce.

John R. Ellement of the Globe staff contributed to this report. Frank Phillips can be reached at phillips@globe.com. Matt Viser can be reached at maviser@globe.com.