U.S. Rep. Alexandria Ocasio-Cortez, D-New York, announced her endorsement Tuesday of Jessica Cisneros, the primary challenger of U.S. Rep Henry Cuellar.

Her move bestows Cisneros with more high-profile support from the progressive wing of the Democratic Party. Since she launched her campaign, Cisneros, a 26-year-old immigration attorney from Laredo, has garnered notable endorsements from presidential candidate and U.S. Sen. Elizabeth Warren, Emily’s List and the Sunrise Movement.

Ocasio-Cortez’s endorsement was largely anticipated. Cisneros is running with the support of Justice Democrats, the progressive organization that backed Ocasio-Cortez in 2018.

“The people of South Texas deserve a Democrat like Jessica who is going to fight for real people, not big corporate donors like the Koch Brothers, GEO Group, and Exxon. When Jessica is elected, not only will I no longer be the youngest person in Congress — I’ll have a strong new ally in the fight for Medicare for All, getting corporate money out of politics, and fixing our broken immigration system,” Ocasio-Cortez said in a statement.

Cisneros is arguing that Cuellar is too moderate for the 28th District, calling him President Donald "Trump's favorite Democrat." Cuellar is denouncing the challenge as meddling by out-of-state partisans who do not truly understand the district. In a statement Tuesday, Cuellar spokesman Colin Strother said the campaign "is going to be decided by voters from the border, not the Bronx."

"We feel confident that our focus on the voters of the 28th District, not PACs and celebrities from out of state, is the best strategy for us," Strother said. "Considering that our opponent only moved to the district four months ago, it isn't surprising that she is completely lacking when it comes to understanding the people [or] the issues of this district."

Cisneros was born and raised in Laredo, and moved back to the district this year after completing law school at the University of Texas at Austin.

Ocasio-Cortez is the first Democrat in the House to support Cuellar’s challenger.

Cuellar, meanwhile, has the backing of party leadership. At The Texas Tribune Festival in September, House Speaker Nancy Pelosi voiced strong support for Cuellar, adding that she is “very, very proud of Henry's work in the Congress, and I'm proud to support him — even if I didn't have a policy of endorsing incumbents." Cheri Bustos, the head of the House Democrats' campaign arm, said Cuellar “is going to be fine,” rejecting the notion that his seat is at all vulnerable.

Editor's note: This story has been updated to note that Cisneros was born and raised in Laredo.

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