Sen. Bernie Sander (I-Vt.) is pushing the Democratic National Committee to vote on a resolution to stop the spending of super PACs in primaries, ahead of the party’s winter meetings this week.

“The Democratic Party must not allow Oligarchs and their super PACs, often aligned with Republicans, to buy Democratic Party primaries,” Sanders said in a letter to DNC Chairman Jaime Harrison and other party leadership. “I believe strongly that there should be public debate and a vote on this important measure.”

Sanders, who built a lucrative grassroots donor network during his two campaigns for president in 2016 and 2020, has called on the party to ditch super PAC spending in the past. However, the organization did not vote on the measure at its last meeting.

Now Sanders is reigniting his pitch to the DNC to consider the measure, saying conservative PACs funded by right-wing billionaires have waded into Democratic primaries to tip the scales against progressive candidates. 

“In the last election cycle, right-wing billionaires funded millions of dollars in spending against progressive candidates in competitive primaries,” Sanders said in the letter. “Those funds were often used by super PACs to run outrageous and dishonest attack ads.”

Sanders’s campaign against super PACs is not a new stance for the independent senator who caucuses with Democrats. The progressive has long been a critic of wealthy donors in political campaigns.

The DNC did not immediately respond to a request for comment.