Representative Christian Menefee defeated Representative Al Green on Tuesday, according to The Associated Press, in a Texas showdown that represented the kind of generational clash consuming the Democratic Party nationwide.

Mr. Menefee, 38, toppled the 11-term incumbent, Mr. Green, 78, in a new Houston district that Republicans redrew last year, compressing two Democratic-held districts into one as they sought to increase Republican seats in the state.

Mr. Green became the first incumbent Democrat to lose a primary in 2026. A series of other generational challenges is set to unfold in the coming weeks and months, including next week in California.

Mr. Menefee first won a special election to fill a congressional vacancy in February. He immediately continued campaigning to stay in Congress, putting him on a collision course with Mr. Green, who has been an outspoken progressive known for heckling President Trump during his speeches before Congress.

Republican mapmakers shifted Mr. Green’s Ninth District from south of Houston to the city’s suburbs, making it solidly Republican. He opted to run for re-election in the new Texas 18th, which Mr. Menefee began representing only a few months ago and which overlapped with some of his old seat.

The race pitted two Black progressives against each other. Even though he had just arrived in Washington, Mr. Menefee, who previously served as the Harris County attorney, scored the endorsement of the Congressional Progressive Caucus PAC.

By far the biggest spender in the race was a super PAC aligned with the crypto industry, which poured more than $5.7 million into the race, partly to make an example of Mr. Green, who is a critic of the industry and sits on the powerful House Financial Services Committee

In a speech on the House floor in May, Mr. Green ripped the industry and called those in his party who sided with it “Cryptocrats.”

“I rise as an unbought, liberated, unafraid Democrat, unbought by crypto cash,” he declared in the speech.

Mr. Menefee initially edged ahead of Mr. Green in the first round of voting in March, but because neither had 50 percent, the race went to a runoff.

The 18th District boasts a storied legacy of prominent Black representatives, including Mickey Leland and Barbara Jordan. In the two years before Mr. Menefee’s election, two of the previous occupants of the seat, both in their 70s, died in office.