PROVIDENCE, R.I. (WPRI) — U.S. Sen. Bernie Sanders announced Thursday he’s endorsing Aaron Regunberg for Congress, giving the former state lawmaker another boost as he seeks to supplant Sabina Matos as the frontrunner in the Democratic primary.

The Vermont senator and two-time presidential candidate joins an expanding list of progressive organizations and elected officials backing Regunberg, one of 12 Democrats vying for the nomination to succeed David Cicilline. The primary is Sept. 5.

“I’m endorsing Aaron Regunberg for Congress because he understands the vital need to stand up against large corporations who have too much control over political and economic systems,” Sanders said in a statement.

Sanders ticked off a number of policies where he and Regunberg agree, including health care, climate change and paid sick days.

“Aaron’s candidacy is about making our government work for everyday people, rather than corporations and billionaires, and he deserves your vote,” he said.

Sanders previously endorsed Regunberg in the latter’s near-miss 2018 Democratic primary challenge against then-Lt. Gov. Dan McKee, while Regunberg helped organize Rhode Island supporters for Sanders’ White House bids in 2016 and 2020.

Regunberg described himself as “deeply honored” by the latest endorsement, saying, “Bernie Sanders is an American hero.”

The intervention by Sanders comes as the 1st Congressional District primary has suddenly shifted into higher gear, with only three weeks left before the start of early voting on Aug. 16.

Matos’s campaign has been rocked by a scandal over forged signatures on her nomination papers, which she has blamed on a hired hand who submitted the paperwork. A criminal investigation into the signatures is under way, but Matos will still be on the ballot.

On the airwaves, Matos and another leading Democratic candidate — former White House staffer Gabe Amo — both began airing their first TV commercials Tuesday and said they planned to continue doing so through the primary.

Regunberg joined the broadcast advertising blitz Wednesday, going on TV with two 30-second ads reinforcing his pitch to progressive voters.

The first commercial — entitled “Together” — features testimonials about Regunberg from five female elected Democrats who have worked with him in the past: state Reps. Cherie Cruz, Leonela Felix, Susan Donovan, and Kathy Fogarty, and Providence City Councilor Sue AnderBois.

The second commercial — entitled “Progressive Fighter” — highlights the endorsement from Sanders and emphasizes Regunberg’s support for policies such as Medicare for All and the Green New Deal.

Regunberg’s campaign said his TV buy will total over $300,000 through Sept. 5, giving him the biggest broadcast advertising budget announced so far. Matos has reserved $280,000 in TV time, while Amo has reserved about $215,000.

“This is one of the most affordable media markets in the country, so your contribution makes a big difference,” Matos wrote in an email to supporters Wednesday. “But we’re being outraised by our opponents so funding our ads is no small task.”

Amo said Tuesday, “This campaign is fundamentally about who can Rhode Islanders trust to advocate for us and get things done. I’m excited to highlight my experience.”

A fourth Democrat — Jamestown lawyer and academic Don Carlson — issued a news release Tuesday saying his campaign had reserved $115,000 of TV time beginning in mid-August. However, Carlson’s campaign is expected to go on the air sooner than that.

None of the other eight Democrats has announced plans to go up on TV so far, but one of them — U.S. Navy veteran Walter Berbrick — announced an endorsement from the progressive group VoteVets PAC.

“Walter Berbrick embodies the spirit of service, always putting his country and community above himself and committing to helping communities in a changing world,” Jon Soltz, the PAC’s chairman, said in a statement.