SAN ANTONIO — By the time Dr. Hector Gonzalez arrived in Laredo, Texas, in 2001, the last abortion clinic had already closed. He spent the next 20 years experiencing firsthand where the largely Hispanic and heavily Catholic community along the border with Mexico usually sided.

“Definitely it was, ‘No abortion,’” said Gonzalez, the city’s former public health director.

That culture has helped protect the region’s nine-term congressman, Henry Cuellar, who is one of the last anti-abortion Democrats in Congress. But he’s facing the stiffest challenge of his career on Tuesday in a runoff election against progressive rival Jessica Cisneros, a 28-year-old immigration attorney who supports abortion access.

With the U.S. Supreme Court poised to potentially overturn abortion rights in a ruling this summer, the runoff is being closely watched for clues about whether the issue will animate Democratic voters. An infusion of money that outside groups have poured on the ground and across TV in South Texas is an indicator of an important race, with abortion rights advocates trying to lower expectations about broader implications.

“National trends are not set by one election and not determined by one election,” said Laphonza Butler, president of Emily’s List, which backs women who support abortion rights and has endorsed Cisneros.

Regardless, the race will provide insight about the direction of the Democratic Party. Progressives have scored some notable wins so far this primary season, defeating a moderate candidate in last week’s Senate primary in Pennsylvania and potentially unseating an incumbent congressman in Oregon, where vote counting is still underway.

Eager to protect an incumbent, House Speaker Nancy Pelosi has stood by Cuellar even as she reaffirms her staunch support of abortion rights. Rep. Jim Clyburn, the third-ranking Democrat in the House, campaigned with Cuellar in Texas this month, saying the most important priority should be keeping the seat in the party’s hands. Cisneros, he argued, was at risk of losing to a Republican.

Still, a leaked draft of the court’s ruling in April has shaken up what was already a close — and increasingly costly — race. In the March primary, Cisneros finished roughly 1,000 votes behind Cuellar, forcing the runoff after neither candidate met the majority threshold to win outright. It was as close as Cuellar has come to losing his 17-year grip on the seat.

But the runoff has also illustrated the uphill climb America’s abortion rights movement faces this fall in mounting an all-out attack on opposing incumbents — a challenge that is on display even here in a solidly Democratic region, to say nothing of the fight ahead in Republican-leaning districts.

The outcome could reveal the limits of abortion as a galvanizing issue for voters. National polling before the leaked draft found abortion trailing other concerns, including high inflation and gun control.

“People here are pretty liberal,” said Martha Cerna, 76, a retired schoolteacher in San Antonio who supports abortion access. “But the further south you go in Texas, the worse it gets.”

Cerna lives in a slice of Cuellar’s district that is more than a two-hour drive north of his hometown of Laredo. She had showed up early in downtown San Antonio for an abortion-rights march and took shade from the blazing South Texas sun in a plaza outside City Hall, where the current mayor and a predecessor, former presidential candidate Julian Castro, are outspoken for abortion rights.

Cisneros joined the march, but Cerna said the voters around here aren’t the ones who need convincing. “That’s why I think it’s going to be a hard sell for her, because there will be some Democrats that are going to want to go with Cuellar,” she said.

Cisneros, who once interned for Cuellar but now carries the endorsements and agenda of Democrats’ left wing, has leaned into the contrast over abortion in the final weeks.

When a grand jury in South Texas indicted a woman on murder charges in April over a self-induced abortion, it happened in one of the district’s rural counties. The charges were swiftly dropped after drawing national outrage, but Cisneros pointed to it as a case of prosecution for seeking health care.

“When we take the time to talk to people about what it really means to be pro-choice, meaning believing government shouldn’t be in the middle of these type of private decisions and seeking abortion, then people usually realize that they’re pro-choice,” she said in an interview.

Cuellar brushed off the impact of the Supreme Court leak at a San Antonio rally this month, saying voters know his position. His powerful allies in Congress have defended their support for Cuellar, in part by saying a loss would open the door to Republicans flipping the district that also leans more conservative when it comes to gun rights and border security.

In Laredo, where Cuellar’s brother is the county sheriff, Gonzalez recalls taking “a lot of heat” when his health department began offering contraceptive pills. He retired in 2019 and expressed disappointment that women seeking abortions had to drive hours either to the Rio Grande Valley — which now has the only clinic on the Texas-Mexico border — or San Antonio.

At a food truck outside San Antonio, Citi Ramos, 64, teared up describing her opposition to abortion while taking a break from serving tacos and burgers to customers. She called herself a Democrat and strong Catholic who typically doesn’t get involved in politics. But, she said, Cisneros’ position is one she can’t sit out.

“I’m pushing everybody to vote,” she said. “It’s a strong issue for me.”