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CNN —  

Sen. Elizabeth Warren on Monday endorsed Jessica Cisneros, the 26-year-old primary challenger to Democratic Rep. Henry Cuellar, in Texas’$2 28th congressional district – a move that could boost Warren’s standing with progressives around the country.

Cisneros, a human rights and immigration lawyer, launched her campaign in June with the support of Justice Democrats, the group that recruited and helped Rep. Alexandria Ocasio-Cortez win her own longshot primary bid in New York last year.

Hillary Clinton won the Texas district, which stretches south from San Antonio to the US-Mexico border, in 2016 by nearly 20 percentage points despite losing the state by 9. The district’s liberal tilt, contrasted with Cuellar’s more conservative voting record, has made the Blue Dog Democrat a target for progressives. He has a 15% rating from NARAL, the abortion rights group, and has been criticized for taking donations from the NRA.

Warren also endorsed Marie Newman, who will again challenge anti-abortion Democratic Rep. Dan Lipinski next year after falling just short of unseating him in a 2018 primary.

“At a time when women’s reproductive rights are under attack daily from Republican lawmakers across America, Illinoisans deserve a leader with an unwavering commitment to fighting for women’s access to reproductive health care,” Warren said in a statement about the race in Illinois’$2 3rd Congressional District.

Newman now has the support of two primary contenders, Warren and Vermont Sen. Bernie Sanders, who also backed her in 2018. New York Sen. Kirsten Gillibrand and Washington Gov. Jay Inslee endorsed Newman before dropping out of the presidential race.

But Warren is the first top Democratic hopeful to throw her weight behind Cisneros.

“The people of Texas’$2 28th district are ready for systematic change and deserve a Democrat that will be on the side of working people; not the side of big money and obstructionist Republicans,” Warren said in a statement provided by the Cisneros campaign.

The Massachusetts Democrat added: “Jessica knows our diversity is our strength and that when progressives are unapologetic about our values and who we’re in this battle for, we win. It’s time Texans had a champion in Congress who does just that.”

Cisneros is running a platform that mirrors the one being promoted by Warren and Sanders, the leading progressives in the 2020 Democratic presidential primary.

She is a supporter of “Medicare for All,” the Green New Deal, new gun control legislation and comprehensive immigration reform. Cisneros has also pledged to rejected corporate campaign contributions.

For Warren, the endorsement is another step in her efforts to corral support from the party’s energetic progressive activist wing.

“At a time when the DCCC is rallying around a pro-NRA and anti-choice Democrat like Cuellar, it’s a breath of fresh air to have leaders in our party stick their necks out for progressive primary challengers fighting for a bold vision,” Alexandra Rojas, executive director of Justice Democrats, told CNN on Monday shortly after the announcement.

Cisneros praised Warren and echoed the Massachusetts senator’s campaign promise to push back against the influence of deep-pocketed corporate interests.

“I’m so proud to receive this endorsement from Senator Warren, who has dedicated her career to fixing our corrupt political system and fighting for working families like mine,” Cisneros said in a statement. “Our district deserves to be represented by a true Democrat who will work in Washington to improve the lives of her constituents, not corporate donors. Senator Warren’s support demonstrates that we’re building the momentum we need to bring real change to South Texas.”

Cuellar, who first took office in 2005 and has argued that the district is more moderate than its voting record might suggest, won reelection in the 2018 midterms with more than 84% support. The primary is scheduled for March 3 of next year.