Boston City Councilor Ayanna Pressley delivered another stunning upset to the Democratic establishment Tuesday night, defeating Rep. Mike Capuano, who conceded defeat in the party’s primary for Massachusetts’ 7th District.

Despite Capuano’s long list of progressive credentials, Pressley seized on an energy among the Democratic base. Progressive groups have battled with party establishment over how best to win back majorities in Congress, arguing Democrats should back more electrifying, young, and diverse candidates.