(CNN) Sen. Elizabeth Warren on Monday endorsed Jessica Cisneros, the 26-year-old primary challenger to Democratic Rep. Henry Cuellar, in Texas' 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' 3rd Congressional District.

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