A long-established and well-known progressive organization is taking on the Democratic Party over a new policy intended to protect congressional incumbents and freeze out challengers.

The new policy, articulated Friday by the Democratic Congressional Campaign Committee, warns vendors that the party will no longer do business with shops which also perform work for primary challengers.

The DCCC, the arm of the party concerned with electing Democrats to the US House, says it has instituted this new policy because its officials believe its “core mission” includes “supporting and protecting incumbents.”

Vermont-based Democracy For America (DFA) objects to the new policy, calling it “the most anti-democratic thing” ever done by the DCCC.

Had this policy been in place last year, it certainly would have hamstrung successful primary challengers like Reps. Alexandria Ocasio-Cortez (D-NY) and Ayanna Pressley (D-Mass.), each of whom won their seats last year only after defeating a long-standing veteran Democrat in a primary election.

“The DCCC is trying to create an atmosphere where vendors are terrified to work with primary challengers — and where primary challengers can’t find the help they need to run strong, effective, successful campaigns,” DFA Political Director Karli Wallace Thompson said in an email to supporters.

“This move isn’t happening in a vacuum,” Thompson added. “At a time when former primary challengers like AOC and Ayanna Pressley — both of whom DFA endorsed and supported — are shaking things up in Congress and making the old guard uncomfortable, it’s no coincidence that the establishment and their consultants are trying to snuff out future primary campaigns before they even begin.”

Thompson also solicited fundraising from supporters who received the email, ostensibly to provide support to those progressive Democratic challengers who would be stifled as a result of the new DCCC policy.

“DFA provides a strong support system for progressive candidates who are trying to bring the voices of working families to Congress,” Thompson said. “And we’re not going to stop fighting to elect a new generation of leaders, no matter how the DCCC tries to rig the game.”