In their first formal event all on one stage, the seven Democrats vying to succeed Edward J. Markey in Congress, together conveyed a clear message to an audience at Watertown Middle School: their positions on many issues are liberal and they are very polite.

At the cordial, policy-heavy forum that sometimes delved into granular, wonkish detail, each candidate worked to softly differentiate himself or herself from the others on the crowded stage, but none used sharp words or personal attacks in the process.

The almost two-hour event saw the candidates address issues from the environment to Syria to revelations about NSA surveillance to entitlement reform.

Advertisement - Continue Reading Below

Despite the low-key vibe, three issues elicited passionate responses from candidates: the Supreme Court’s Citizens United Decision, the debate over US forces intervening in Syria, and gun control.

Citizens United, which allowed for unlimited spending on elections by corporations and labor unions, was one of the few areas of light disagreement during the forum, which was sponsored by the Belmont and Watertown Democratic town committees.

Most of the candidates voiced strong support for a constitutional amendment to undo the controversial 2010 decision from the high court.

“I think Citizens United has the potential to unravel our very Democracy,” said state Senator Katherine Clark of Melrose. “Corporations are not people and we have to make sure that is reflected in the Constitution of our country.”

State Senator Karen Spilka of Ashland called the ruling a “terrible decision” that should be overturned.

“I think it’s really critical that we don’t give up on a Constitutional Amendment,” said state Representative Carl M. Sciortino.

But state Senator Will Brownsberger, who said he doesn’t accept contributions from political action committees or lobbyists, took a different view.

“The fundamental problem of American politics did not start with Citizens United,” he said, it “started with who we elected and what we expect of them.”

He framed “the call for the reversal of Citizens United [as] something that serves to distract.”

“I respectfully disagree with Will,” Middlesex Sheriff Peter J. Koutoujian said. “The fact is these are unregulated, unlimited, non-transparent funds that are flowing into elections.”

“The Constitution says ‘We the people,’ not ‘We the corporations,’” he said.

The debate ended shortly before President Obama addressed the nation about Syria.

In responding to a question about when a humanitarian intervention is called for, Spilka and Koutoujian both cited their personal heritage. Spilka, who is Jewish, said she had family members who died in the Holocaust. Koutoujian, “the grandson of Armenian Genocide survivors,” said the issue was more emotional than political.

Prior to the forum, all the Democratic candidates except Spilka had expressed opposition to authorizing Obama to use military force in Syria. Spilka did not take a hard position on the issue during the event.

Candidates also staked out similar positions on gun control, with many voicing support for measures like universal background checks.

But Koutoujian and Clark both were particularly animated on the issue.

“You know, we’re losing 56 children a week to gun violence,” he said, adding that gun control legislation would be a priority for him in Congress.

“We can beat the NRA,” she said.

The forum, held five weeks before the Oct. 15 special primary election, was moderated by George Bachrach, a former state Senator.

Given the number of hopefuls and the limits of time, Bachrach sometimes politely pushed candidates to finish their thoughts.

As Martin Long, an Arlington author, was expounding on his support for single-payer health care, Bachrach moved to let another candidate speak.

“Ok,” he interjected.

“I’ve got lots more to say,” Long replied.

“It’s a large table,” Bachrach said.

Long, one of two candidates who is not a current elected official, repeatedly worked to emphasize he was different from most of his opponents, framing himself as “a candidate of ideas.”

“I am not a professional politician looking for promotion,” he said toward the end of the forum, perhaps the most potent attack, indirect though it was, of the evening.

But there were emotional moments form other candidates as well. Koutoujian and Brownsberger both appeared to tear up talking about their votes in favor of marriage equality which they both called the proudest moment in their careers.

Also at the debate was Stoneham resident Paul John Maisano, who works in the construction industry, though he spoke less than his six opponents.

“I bring a different perspective to this room. I bring a perspective from the streets, from people who are out there hustling out there every day,” he said. “I’m a candidate for the working person.”

The elected officials also worked to paint themselves as different from the others seated next to them.

“Since I’ve been in the State House, I’ve taken on the special interests that nobody else wanted to take on,” Spilka said. “I’m known as a fighter on Beacon Hill,” she added, making the case for why voters should pick her to represent the district of more than 700,000 people.

The mostly-suburban district, which runs from Winthrop to Woburn to Southborough to Holliston, is heavily Democratic so the winner of the party’s primary will be the favorite in the Dec. 10 special general election.

There are three Republicans running for their party’s nomination: actuary Tom Tierney of Framingham, Harvard nanophysics researcher Mike Stopa of Holliston, and businessman and lawyer Frank J. Addivinola Jr. of Boston.

The Congressional seat was vacated after Markey was elected to the US Senate, succeeding John F. Kerry, who had become Secretary of State.