NEWTON, Mass. (WPRI) — Seven of the candidates seeking to replace Democratic Congressman Joe Kennedy III met Tuesday night for their first debate of the campaign, getting an early chance to differentiate themselves in a crowded but geographically limited field.

The seven Democrats — Brookline residents Alan Khazei, Jesse Mermell, Dave Cavell, Ihssane Leckey and Ben Sigel, and Newton residents Jake Auchincloss and Becky Grossman — met at an event hosted at Boston College Law School by The Gavel, a progressive student publication at BC.

Kennedy is giving up the 4th Congressional District seat — which stretches from Boston’s wealthy suburbs down through the Attleboros and Taunton into Fall River — to challenge incumbent U.S. Sen. Ed Markey.

The two-hour exchange stayed polite throughout. While there was broad agreement on many of the big issues discussed, from health care and transportation to President Trump’s record, Auchincloss and Leckey drew some of the clearer distinctions.

Auchincloss, a 32-year-old Newton city councilor who emphasized his service in Afghanistan as a Marine, promoted a more moderate policy agenda than his rivals. He argued Democrats need to examine expanding nuclear power to combat climate change, and questioned some of the left’s priorities, including tuition-free college and eliminating private health insurance to institute Medicare for All.

On health care, Auchincloss warned of the possibility Massachusetts could jeopardize its first-in-the-nation universal system as well as its life sciences industry.

“We have to be very careful as a state not to introduce federal legislation that will undermine a really important driver of our economy and potentially take us backwards,” he said.

Leckey, a 34-year-old former Federal Reserve official, is the only candidate who entered the race while Kennedy was still a candidate, having planned to challenge the incumbent in the primary.

A self-identified democratic socialist, Leckey offered the strongest echo of Bernie Sanders’ surging presidential campaign, describing herself as “100% aligned” with the Vermont senator. She defended the same policies Auchincloss questioned, including a Sanders-style Medicare for All system, and accused the others of promoting “incrementalism.”

On two raise-your-hands questions from the moderators — about support for single-payer health care and tuition-free college — Leckey was both times joined in expressing support by Mermell, a 39-year-old former Brookline Select Board member and top adviser to Gov. Deval Patrick.

But Mermell argued she would be skilled at coalition-building in Congress thanks to her experience in the Patrick administration, as leader of of a progressive business organization, and as a top staffer in Planned Parenthood’s Massachusetts chapter.

“It’s about more than just being a good vote — it’s about being a champion,” Mermell said.

Cavell, a 35-year-old former aide to Patrick and assistant attorney general under Maura Healey, also raised his hand in support of tuition-free college, admitting that he and his wife have roughly $300,000 in student loan debt combined.

Cavell said his “day one” issue if elected to Congress would be the opioid crisis, a priority he said is driven by his work on the lawsuit filed by Healey against opioid manufacturer Purdue Pharma and its controlling family, the Sacklers. He also repeatedly tried to bring the conversation back to a contrast with the national Republican agenda.

Khazei, 58, the fundraising leader in the race so far, cited his work founding the service program City Year as inspiration for how he would work on Capitol Hill. “There is a new people-powered progressive politics movement that is rising up in our district and in our country and that is the key to taking our democracy back,” he said.

Among Khazei’s distinguishing ideas: tying additional college funding to a year of national service.

Grossman, 39, another Newton city councilor and another leader in raising money, prioritized gun legislation and battling the National Rifle Association, describing her horror at the active shooter trainings her young children have had to go through.

“I am running for Congress with the fierce urgency of a mom who is fed up with what is going on in the country,” she said, echoing a comment she makes on the campaign trail.

Sigel, a lawyer from Brookline, was the newest entrant in the race on stage. Noting that he would be the first Latino ever elected to Congress in Massachusetts, he highlighted his work to bring together diverse communities as a strength he would bring to Washington. “We need a leader who’s a bridge-builder,” he said.

On politics, all the candidates expressed varying levels of support for keeping Nancy Pelosi as House speaker if Democrats retain the House. But Auchincloss said he would be open to alternatives if the party takes back the White House, while Leckey suggested Pelosi should be more supportive of the group of progressive women lawmakers known as “the Squad.”

As for the presidential race, Mermell and Cavell are backing U.S. Sen. Elizabeth Warren, Leckey is supporting Sanders, and the others declined to choose a candidate — though Sigel acknowledged time is running short since the Massachusetts primary is next Tuesday.

Two other 4th District candidates — Democrats Tom Shack and Herb Robinson — have also filed paperwork to run but were not at the debate.

Watch the full debate here:

Ted Nesi (tnesi@wpri.com) is WPRI 12’s politics and business editor and a Target 12 investigative reporter. He is a weekly panelist on Newsmakers and hosts Executive Suite. Follow him on Twitter and Facebook