By Moira Warburton
WASHINGTON (Reuters) -Centrist U.S. Representative Henry Cuellar was clinging to a razor-thin lead early on Wednesday against progressive challenger Jessica Cisneros in a high-profile south Texas Democratic primary battle that illustrated sharp dividing lines over immigration and abortion rights.
The election on Tuesday in a district along the U.S.-Mexico border was the third contest between Cuellar, who has held the seat since 2005, and Cisneros, a 28-year-old attorney who failed to unseat him in 2020 but forced him to a runoff in the state's March primary this year.
A tally by Edison Research showed Cuellar up by just 177 votes with 92% of the estimated vote counted. Major media outlets held off on calling the race.
Despite the slim margin, Cuellar declared victory. Cisneros, however, declined to concede, saying every ballot needed to be counted.
The race took on new urgency in recent weeks after a leaked Supreme Court opinion indicated that it could overturn a 1973 ruling that legalized abortion nationwide.
Cuellar, 66, is the lone House Democrat to oppose abortion rights, and abortion-rights groups have spent at least $160,000 to bolster Cisneros' campaign.
Cuellar has said that Cisneros would risk public safety and hurt the local economy by cutting law enforcement funding in a district where many voters work for border patrol agencies.
Cisneros has since distanced herself from her previous call to eliminate U.S. Immigration and Customs Enforcement.
Political analysts have said that a Cisneros win could threaten Democrats' chances to hold the seat in the Nov. 8 election, when Republicans hope to win control of the House of Representatives.
But Cuellar's strength in the general election should not be a foregone conclusion, said Joshua Blank, research director of the Texas Politics Project at the University of Texas in Austin.
"The reality is that Cisneros has come very close to unseating Cuellar twice at this point," Blank said. "If he can't defeat Cisneros, then I think the logic underlying that should come into question."
Cisneros has benefited from increased name recognition and an FBI investigation that saw raids on Cuellar's home and office.
Financial disclosures on Friday showed she has out-raised him by almost $1.4 million, and has around $400,000 more cash on hand than Cuellar.
The race is one of several midterm primary battles between incumbent House Democrats and progressive challengers.
In primary contests last week, Jamie McLeod-Skinner looks set to oust moderate incumbent Kurt Schrader in Oregon, while progressive Summer Lee won the Democratic nomination over Steve Irwin in Pennsylvania's 12th Congressional District. Other progressive challengers like Nina Turner in Ohio have lost.