SEEKONK, Mass. (WPRI) — Democrat Jesse Mermell has snagged one of the last big endorsements still to be won in the southern half of Massachusetts’ 4th Congressional District.

State Sen. Paul Feeney, a Foxboro Democrat, announced Thursday he is throwing his support behind Mermell in the eight-way Democratic primary to succeed Congressman Joe Kennedy. The 4th District stretches from northern Fall River through the Attleboros and Taunton up to the Boston suburbs.

With all eight Democratic candidates hailing from either Newton, Brookline or Wellesley, there has been fierce competition among them to land key endorsements in Bristol County as a way to prove their bona fides to voters who live nearer to Providence than Boston.

Feeney said he’s been in touch with all the candidates, describing the primary slate as “a talented field of individuals.” But he said in recent weeks he’d been hearing from an increasing number of his own supporters and constituents encouraging him to get behind Mermell.

“I have heard from so many of them that said, ‘Paul, Jesse is the real deal.’ And I agree with them,” Feeney told WPRI 12 on Thursday.

Mermell, a former Brookline Select Board member and top aide to Gov. Deval Patrick, said she was elated when Feeney called her Wednesday to share his decision.

“I’m not naive to the political significance of this endorsement, but it means more to me personally because I know what Senator Feeney’s values are, I know how hard he fights for working families, I know how hard he fights for a health care system that works for everyone, and to have him in my corner, to have him place his faith in me, means the world,” she said.

Feeney — whose state Senate district stretches from Seekonk and Rehoboth as far north as Medfield — seriously considered running for the 4th District seat himself last year but ultimately decided to remain on Beacon Hill. His endorsement could help Mermell in part because he has ties to multiple wings of the party, as a union ally who’s been a high-profile supporter of both Bernie Sanders and Joe Kennedy.

“It’s incredibly important,” said Mermell, who is battling other Democrats including Ihssane Leckey and Natalia Linos for the support of progressive voters.

Feeney’s announcement comes one day after New Bedford Mayor Jon Mitchell endorsed one of Mermell’s leading rivals, Newton City Councilor Jake Auchincloss, whose campaign has made it a priority to seek an edge in Bristol County. While New Bedford isn’t part of the 4th District, Mitchell said voters’ choice in the race will affect all of Southeastern Massachusetts.

Mermell dismissed the idea that Auchincloss is gaining an edge in the South Coast. “I think he should be worried that we’re running up the score in the southern part of the district,” she said, ticking off her support from officials in Fall River and Taunton as well as various unions and activist groups.

With 12 days to go, Mermell said her campaign team remains focused on grassroots organizing. “We’re feeling good about how our hard work is going to pay off,” she said.

The in-person early voting period for the primary starts Saturday and continues through Aug. 28. Voters who want to cast a ballot by mail must have their applications in by next Wednesday and return them by 8 p.m. on Sept. 1.

The Democratic nominee will go on in November to face the winner of the 4th District Republican primary between Julie Hall and David Rosa.

Watch the 4th District candidates debate earlier this week:

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