In this May 14, 2020, file photo, Rep. Joe Kennedy III, D-Massachusetts, asks questions during a committee hearing on Capitol Hill in Washington. Credit: Greg Nash / AP

BOSTON — The Democratic primary contest between U.S. Sen. Edward Markey and U.S. Rep. Joe Kennedy III may be the most closely watched campaign on the Massachusetts ballot this year, but it’s far from the most crowded.

That distinction goes to the race for the state’s 4th Congressional District seat — the seat Kennedy is vacating.

Ten candidates — eight Democrats and two Republicans — are vying to represent the district that winds from the Boston suburbs of Newton and Brookline south through Attleboro, Taunton and Fall River. It was previously represented by former Democratic U.S. Rep. Barney Frank.

Democratic candidates include Jake Auchincloss, Becky Grossman, Alan Khazei, Natalia Linos, Isshane Lecky, Jesse Mermell, Ben Sigel and Chris Zannetos. A ninth Democrat, Dave Cavell, suspended his campaign Thursday.

Whoever wins the Democratic primary will be considered the favorite in the November general election in the heavily Democratic district.

Two Republicans are also running — Julie Hall and David Rosa.

The candidates hail from a range of backgrounds. They include former members of the military, immigrants, political veterans, entrepreneurs and those with backgrounds in the nonprofit sector.

The race is also the first for an open seat in Congress in Massachusetts since the surprise win by Democratic U.S. Rep. Ayanna Pressley in 2018, who defeated incumbent Democratic U.S. Rep. Michael Capuano.

All the Democratic candidates live in the northern, wealthier tip of the district, with two hailing from Newton, one from Wellesley and five from Brookline.

Auchincloss served as a captain in the U.S. Marines in Afghanistan in 2012 and led an anti-narcotics platoon in Panama in 2014. He was elected to the Newton City Council in 2015.

Auchincloss has said he wants to help rebuild the country that sent his grandfather — “a poor Jewish kid” — to college during WWII. As of June 30, Auchincloss reported raising nearly $1.4 million with more than $1.1 million left in his account.

Mermell is a former Brookline select board member and one-time aide to former Democratic Gov. Deval Patrick. She’s won Pressley’s endorsement and on Thursday also won the backing of Democratic Attorney General Maura Healey.

Mermell has also worked at Planned Parenthood League of Massachusetts where she said providers had to navigate complex federal rules to provide care. “If that isn’t the definition of inequity, I don’t know what is,” she said recently. As of June 30, Mermell reported raising about $834,000 with $448,000 left in her account.

Khazei co-founded City Year with his roommate at Harvard Law School and went on to help create Americorps under the Clinton administration. Khazei also launched two unsuccessful bids for the U.S. Senate in 2010 and 2012.

The Khazei campaign said in an ad that it’s time for “a movement leader” in Congress, saying Khazei has the experience “to change a system that shuts people out.” As of June 30, the Brookline resident reported having raised more than $1.6 million with about $1.1 million left on hand.

Leckey, a self-described democratic socialist, was born in Morocco, immigrated to the United States and became a Wall Street regulator. She’s been endorsed by Minnesota Democratic U.S. Rep. Ilhan Omar.

Leckey, who has said she’s “faced sexual harassment and wage theft,” said she would be the state’s first Muslim and Arab-American member of Congress. As of June 30, the Brookline resident reported raising nearly $964,000 — loaning her campaign $800,000 — with $726,000 left in her account.

Grossman is a member of the Newton City Council and served as an assistant district attorney in Middlesex County. She’s the daughter-in-law of Steve Grossman, former chair of the Democratic National Committee.

She’s described herself as “a mom who is fed up by what’s going on in this country.” As of June 30, Grossman reported having raised about $824,000 with $417,000 left in her account.

Zannetos has created tech and cybersecurity companies. He also founded STEMatchMA, a nonprofit working to foster STEM — science, technology, engineering, and mathematics — education in marginalized communities.

Zannetos said the country “need leaders who understand the technology-driven economy.” The Wellesley resident reported raising nearly $650,000 — loaning his campaign $300,000 — with $506,000 left in his campaign account as of June 30.

Linos is an epidemiologist and the executive director of the FXB Center for Health and Human Rights at Harvard. She describes herself as “a first-generation Greek-American” and has released a 25-page COVID-19 response plan.

As of June 30, the Brookline resident reported raising $202,000 — including a $35,000 loan to her campaign — with $177,000 left in her account.

Sigel has worked for the Democratic National Campaign Committee. For the past eight years, he’s worked as a civil litigation lawyer at the firm Mintz Levin. On June 30, the Brookline resident reported having raised nearly $288,000 with $115,000 left in his account.

Sigel describes himself as “the proud Jewish son of a Puerto Rican mother” and said he would be the first Latino to represent Massachusetts in Congress.

The Republican primary pits Hall, a former Air Force colonel and Attleboro city councilor, against Rosa of Dighton, a veteran and parks and recreation commissioner.

Hall has reported collecting about $8,000 in campaign donations, with $115 left on hand as of June 30.

The primary is Sept. 1.

Story by Steve LeBlanc.