2018 U.S. midterm elections
Democrats won control of the House, and progressive candidates such as Alexandria Ocasio-Cortez won primaries in safe Democratic districts. Moderate Democrats flipped suburban seats that had been Republican.
The party gained subpoena power and a larger progressive caucus.
The two wings fought over health care and climate policy through the 2020 presidential primary.
The same pattern appeared in 2026: a national Democratic wave did not translate into local progressive wins in San Francisco.
