But some challengers lost, and their overall wins were a modest number compared with the 535 House and Senate members.
Kessler wasn't impressed with the three progressive challengers who defeated Democratic incumbents, either.
Other high-profile progressive hopefuls lost Senate Democratic primaries in Colorado, Maine and Texas, and House contests in states including Georgia, New York and Ohio.
Jamaal Bowman, a Black educator raised by a single mom, defeated House Foreign Affairs Committee Chairman Eliot Engel of the Bronx and Westchester, New York.
They're an effective and well-funded operation now," said Sean McElwee, who does polling and research for progressive Democrats.