Colorado’s Democratic primary shake-up is intensifying fears among party insiders that an anti-establishment revolt once seen as concentrated in New York City is rapidly spreading across the country ahead of the 2026 midterm elections.

The defeat of longtime Rep. Diana DeGette (D-CO) in Colorado at the hands of 29-year-old attorney and Ph.D. student Melat Kiros marked the latest warning sign for Democratic insiders already rattled by a string of progressive-backed primary upsets in recent weeks.