Representative Wesley Bell beat Cori Bush, his predecessor, in a rematch. He will be a heavy favorite in the safely Democratic district in November.

© Eric Lee for The New York Times

Former Representative Cori Bush, a member of the progressive “squad,” is trying to defeat Representative Wesley Bell, a moderate who ousted her two years ago.

A wave of outsider fervor has already knocked out a number of incumbents in primary races. Several more face spirited opposition.

© Rebecca Slezak/Associated Press