Twenty-two 'pop-up' super PACs formed shortly before the 2026 midterm elections and together spent about $637 million on U.S. congressional races, according to campaign-finance disclosures. The groups registered late enough in the cycle that their donor lists were not public until after many voters had already cast ballots.

Campaign-finance analysts say the tactic exploits a gap in U.S. disclosure rules: a political committee's first public filing can lag its spending by weeks, letting a late-forming group flood a race with ads before anyone can trace the money. The $637 million figure spans House and Senate contests nationwide.

Election-law groups have urged the Federal Election Commission to tighten reporting deadlines, while some of the PACs' organizers say they followed existing law to the letter. The debate adds to broader scrutiny of outside spending as control of Congress remains undecided heading into the final stretch of the 2026 midterms.