Melat Kiros, a 29-year-old democratic socialist and immigrant, has achieved a significant political victory. She defeated Representative Diana DeGette in the Democratic primary for the Denver area, signaling a strong push by the progressive faction within the Democratic Party.

This victory by Ms. Kiros removes a 15-term incumbent and highlights the power of the insurgent coalition that recently saw success in New York congressional races. Given the solidly Democratic nature of the district, Ms. Kiros is highly likely to win the general election in November.

Ms. Kiros is a lawyer and a doctoral student in public affairs. She positioned herself as an outsider focused on tackling the affordability issues that she argued were ignored by the Democratic establishment. Her campaign’s opposition to U.S. support for Israel was a key element of her platform and political identity.

Despite Ms. DeGette’s financial advantages, bolstered by last-minute spending from external groups, Ms. Kiros’s grassroots campaign secured a lead. By early Wednesday, she was ahead by more than five percentage points with nearly 80 percent of votes counted.

In her campaign biography, Ms. Kiros recounted an incident with a Manhattan law firm where she previously worked. In 2023, the firm dismissed her after she refused to remove a letter questioning Israel’s historical legitimacy and supporting pro-Palestinian protesters. She also challenged the firm’s treatment of activist law students, reflecting her commitment to her political beliefs.