House Democratic leaders have spent the past few weeks waging a bitter campaign against their own left flank over a leftwing streamer. On Tuesday, it was the party’s center-right who blindsided them.

Hakeem Jeffries, the House minority leader, announced late on Tuesday that he had asked the Democratic caucus’s committee on caucus rules to consider punishing the retiring Jared Golden of Maine and Blue Dog Coalition leader Marie Gluesenkamp Perez of Washington after the pair sided with Republicans on a procedural vote that had appeared doomed.

“The decision by two of our colleagues to blindside the entire House Democratic caucus and join with the Republican majority to pass a procedural rule on the brink of failing represents a significant breach of trust,” Jeffries said in a joint statement issued with the Democratic whip, Katherine Clark, and the caucus chair, Pete Aguilar. “It necessitates a serious response, and we have asked the committee on caucus rules to take this up in short order.”

The rebellion lands at an awkward moment for Jeffries. For much of the past few weeks, he and other senior Democrats have trained their fire on the party’s left, repeatedly condemning Hasan Piker, a leftwing streamer, over remarks about antisemitism and the 11 September attacks that he says were taken out of context. That campaign has drawn accusations from progressives that leadership is picking an unwinnable fight with a Twitch personality while ignoring bigger political threats. On Tuesday, the bigger threat to comity turned out to come from the party’s center-right instead.

The vote in question was a routine procedural measure known as a “rule”, which the House majority must pass before it can bring legislation to the floor. Five Republican hardliners had planned to vote it down, in a dispute unrelated to its substance, which would have handed the speaker, Mike Johnson, an embarrassing defeat and potentially disrupted the House’s legislative calendar for the rest of the month.

Golden and Gluesenkamp Perez supplied the votes that let the rule pass, 210 to 208. Under House rules, a tied vote is treated as a defeat, meaning their support was decisive. It is highly unusual for members of the minority party to back the majority’s procedural rules, which typically pass on party-line votes and are treated by leadership as a basic marker of caucus discipline.

Neither Golden nor Gluesenkamp Perez gave Democratic leaders advance notice, according to House Democratic leadership. Clark told reporters shortly after the vote that the move “came as a surprise”. Jeffries later told reporters that the two Democrats “blindsided the entire caucus and created a significant breach of trust”.

The rule cleared the way for a package of Republican-favored bills to reach the floor, including a GOP resolution condemning socialism and the Democratic Socialists of America, a measure Republicans are expected to use against Democrats in midterm campaign messaging. That resolution also included a poison pill in the form of a statement of support for Donald Trump’s restrictive voting legislation, Save Act. The stunt was designed to force House Democrats to choose between voting against the resolution in what Republicans would portray as tacit support for socialism, or vote in favor of it and lend a (non-binding) blessing to legislation that experts say could stop millions of Americans from voting.

The rule also advanced a bipartisan bill, co-authored by Golden, to shield Maine’s lobster industry from federal whale-protection regulations the fishing industry says could put smaller operators out of business.

Golden said that bill was his reason for breaking ranks. “I voted for the rule for one simple reason: it paved the way for a vote on my bill to protect Maine lobstermen from costly, burdensome new regulations that would put them out of business,” he said in a statement.

Gluesenkamp Perez, who leads the conservative Democratic Blue Dog Coalition, cited similar concerns for working waterfront communities in her south-west Washington district, jabbing on social media that “what the DC bubble doesn’t get is that working waterfronts require working people”.

Golden, who is retiring at the end of this Congress, has also indicated he had lined up other Democratic votes for the rule beforehand, suggesting the move was deliberate rather than a last-minute miscalculation.

The episode has exposed deeper strains inside a Democratic caucus that has struggled to project unity since its losses in the 2024 elections. Asked whether the two lawmakers would face consequences, Jeffries told reporters on Tuesday that the matter was “under discussion”. By the evening, he, Clark and Aguilar had escalated that to a formal referral.

Axios has reported that stripping Golden and Gluesenkamp Perez of committee assignments was among the options being discussed by frustrated members as a way to “make an example” of the pair, though no decision has been made and it remains unclear what disciplinary powers the committee on caucus rules can actually exercise.

Golden and Gluesenkamp Perez, both first elected in swing or Republican-leaning districts, have each broken with their party before, including on past government funding bills and an earlier version of a Republican voter-fraud measure. Golden co-chaired the centrist Blue Dog Coalition until Gluesenkamp Perez succeeded him in the role.

Johnson, for his part, told reporters after the vote that critics who had predicted his majority would fail to pass the rule “were wrong”.

“The rule has passed,” Johnson said. “Many of you thought that would not happen today, but we passed a rule to continue business this week. Republicans are here to work.”