Under House rules, the motion to recommit is one of the few mechanisms granted to the out-of-power party to shape legislation.

“Controlling the Congressional agenda really is the sine qua non of a successful majority party,” Sarah Binder, a political scientist at George Washington University and a senior fellow at Brookings, told me.

If there is one thing that sets Nancy Pelosi apart from other Democratic speakers, it is her ability to maintain control of the Democratic majority on key votes.

It is no wonder, then, that she was outraged when these 26 moderate Democrats supported a Republican motion to recommit on Feb. 27 — explicitly designed to thwart progressive Democrats who adamantly oppose reporting undocumented immigrants to authorities. To Pelosi, the motion was an aggressive attempt on the part of House Republicans to undermine her leadership, and moderate Democratic members who supported it were seeking political cover at her expense.

“We are either a team or we’re not, and we have to make that decision,” she declared at the Democratic caucus meeting. “This is not a day at the beach. This is the Congress of the United States.”

In recent decades, “the motion to recommit has been weaponized,” Tom Mann, a senior fellow at Brookings, wrote me by email. “Like almost every effort on the floor by the minority party in the face of majority control of the agenda in the majoritarian House, it is an electoral weapon used to divide and weaken the majority.”

Jason Roberts, a political scientist at the University of North Carolina, provided a brief history of the motion in an email. “It was made into a minority right in 1909. It did not really become controversial until the 1970s. Before then, most bills were considered under open rules” that allowed anyone from either party to offer amendments. In the 1970s, Roberts explained, the Democratic majority “began using more restrictive rules that limited or closed off amending opportunities.” This left Republicans with only one alternative to force a vote on an amendment: the motion to recommit.