ATTLEBORO, Mass. (WPRI) — Progressive groups sent a billboard truck to protest outside Massachusetts Congressman Jake Auchincloss’s district office on Tuesday, in a bid to call attention to his disagreement with House Speaker Nancy Pelosi over drug prices.

The groups Social Security Works and Organize for Justice paid for the truck to circle outside the Bronson Building at the corner of North Main and County streets in Attleboro, with a picture of Auchincloss on the side and a message saying: “Rep. Jake Auchincloss is blocking efforts to lower your drug prices.”

At issue is the Lower Drug Costs Now Act, or H.R. 3, a top priority bill for Pelosi and other House Democratic leaders.

The speaker’s office says the measure would “level the playing field for American patients and taxpayers” by, among other changes, letting Medicare negotiate prices with pharmaceutical companies for certain drugs and limiting out-of-pocket costs to $2,000 for Medicare beneficiaries.

Earlier this month, however, Auchincloss was one of the lead authors of a letter to Pelosi from 10 rank-and-file House Democrats that offered a thinly veiled critique of her approach. The group argued any legislation needs to strike “a balance between innovation and affordability” as well as obtain “buy-in from a majority of Americans and stakeholders in the public and private sectors.”

“As we have just seen with the lifesaving, record-breaking development of COVID-19 vaccines and therapies, America benefits from the most innovative and capable researchers in the world, and from public-private partnership that encourages world-leading biomedical research and development,” they wrote.

With Democrats holding only a razor-thin majority in the House and no sign that Republicans will support the bill, the letter led to a flurry of news coverage on Capitol Hill. Politico’s headline was “Pelosi drug price plan threatened by centrist defections,” while the influential science site STAT wrote, “Key House Democrats demand a ‘bipartisan’ drug pricing bill.”

The coverage raised eyebrows back in Massachusetts, where Auchincloss is seen as potentially vulnerable to a primary challenge from the left in 2022 after he barely defeated rival Jesse Mermell in last year’s 4th District primary to succeed Joe Kennedy III. (Mermell has not yet said whether she plans to seek a rematch next year.)

All nine members of Massachusetts’ all-Democratic House delegation, including Kennedy, voted for the previous version of the Lower Drug Costs Now Act when it came up for a vote in December 2019, as did Rhode Island’s David Cicilline and Jim Langevin, also Democrats.

“There’s nothing ‘moderate’ or ‘bipartisan’ about blocking plans to lower drug prices,” Alex Lawson, executive director of Social Security Works, said in a news release Tuesday. “In fact, lowering drug prices is incredibly popular with voters across the political spectrum. Auchincloss is a shill for pharmaceutical corporations, and we’re making sure his constituents know it.”

Matt Corridoni, a spokesperson for Auchincloss, rejected the criticism. He said Auchincloss supports lowering out-of-pocket costs for Medicare beneficiaries, and emphasized the freshman lawmaker’s differences with Republicans as opposed to with fellow Democrats.

“Democrats are going to pass a drug pricing bill and Congressman Auchincloss is going to help get it done,” Corridoni told 12 News. “The real roadblock is Republicans. Right now, the Democratic caucus is engaged in a healthy policy debate about how best to lower the cost of drugs.”

He added, “There’s nothing more progressive than wanting to make medication cheaper and cure disease.”

Auchincloss’s 4th District stretches from northern Fall River through Taunton and the Attleboros up into Newton and Brookline.