Her marathon monologue — highly unusual for the House, which has no equivalent to the filibuster in the Senate — came as Republicans are scrambling to pass legislation to keep the government open. A short-term funding bill expires on Friday.

Ms. Pelosi has said she will not vote for the measure; she is protesting its lack of protection for the Dreamers, young immigrants brought to the country illegally as children, who have been shielded from deportation by the Deferred Action for Childhood Arrivals program, or DACA, an Obama-era initiative that President Trump has suspended.

Her talk was quickly dubbed the DACA-Buster on Twitter. (Twitter users also noted, in admiration, that six hours in, Ms. Pelosi was still wearing her four-inch heels.)