Cisneros, a former intern in Cuellar’s office making her second run against him, was backed by prominent progressives, including Rep. Alexandria Ocasio-Cortez (D-N.Y.) and Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.). The incumbent, a moderate Blue Dog Democrat, got backing from House Democratic leadership, including Speaker Nancy Pelosi, and a pair of big-spending super PACs.

Cuellar’s win offers a jolt to the establishment-aligned forces that have come together this primary season to back more moderate Democratic candidates and thwart progressives. The South Texas victory would have been a massive win for their adversaries on the left, who have won some other key primaries this spring, including ousting Rep. Kurt Schrader (D-Ore.), another Blue Dog Democrat.

But privately, even some Democrats not ideologically aligned with Cuellar are relieved that he prevailed, because they believe Cisneros’s support for progressive policy positions, such as a Green New Deal and Medicare for All, wouldn’t have played well in the general election in a large battleground district that relies heavily on oil and gas.

Cuellar must win again in November to keep the seat — and Republicans are targeting the district, which President Joe Biden carried by 7 points. The GOP nominee is Cassy Garcia, a former aide to Sen. Ted Cruz (R-Texas).

Garcia is one of three Latina Republicans running for South Texas districts this fall, including Rep.-elect Mayra Flores, who gave the group a boost this week by winning a special election for a vacant Democratic seat that President Joe Biden carried by 4 points in 2020. The November election will take place under new district lines, and national Democrats insisted it was a waste of effort to compete for the soon-to-disappear seat.

Cuellar still won by 19 points in 2020, even as Biden’s margins in his district shrank from the comfortable double digits advantages won by previous Democratic presidential nominees. But the rapid political shifts in South Texas have Republicans hoping they can challenge him this fall.

Cisneros tried to best Cuellar by running up the margins in the more liberal areas of the district in and around San Antonio. And the Supreme Court’s preparations to slash abortion rights added renewed urgency to the race, especially in those areas.

EMILY’s List, a pro-abortion rights group that backs female candidates, made an 11th hour TV buy of $550,000 to help boost Cisneros. By the final weeks of the race, the candidate and the group were together outspending Cuellar and his two allied super PACs on the air.

Cuellar, who said in the aftermath of the publication of the Roe draft opinion that he did not support a total ban on abortion without exceptions, claimed his views were in line with the majority of the Catholic-heavy district. He also said that he was not the FBI raid reportedly linked to a federal probe of Azerbaijan-connected campaign donation.

But Cisneros gained undeniable momentum in the final weeks of the race. After coming about 1,000 votes away from besting Cuellar in the March primary, Cisneros pulled in $1.2 million from April 1 to May 4, according to reports recently filed with the Federal Election Commission. Cuellar raised just $352,000.

But the incumbent had more help overall from two super PACs, one linked to pro-Israel donors and another with ties to LinkedIn co-founder Reid Hoffman.