Harlingen doctor becomes first Democrat to challenge GOP Rep. Monica De La Cruz for South Texas congressional seat

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Ada Cuellar, a Harlingen-based emergency physician, launched her campaign for Texas’ 15th Congressional District on Thursday, becoming the first Democrat to run for the South Texas seat that her party is targeting in the 2026 midterms.

Anchored in Hidalgo County along the border and running north to the edge of San Antonio, the district — represented by Rep. Monica De La Cruz, R-Edinburg — has been emblematic of Democrats’ recent struggles throughout the Rio Grande Valley and with Latino voters generally. De La Cruz first won office in 2022, becoming the first Republican to represent the district after it was redrawn to favor Republicans.

The seat has been in Democrats’ crosshairs ever since. But South Texas was the epicenter of a national rightward shift in 2024 among Latinos, who make up about three-quarters of the 15th District’s eligible voting-age population, according to U.S. Census Bureau data. President Donald Trump was the first Republican to win Hidalgo County in decades, improving from a 28% vote share in 2016 to 51% last year.

Whoever wins the Democratic nomination will likely face an uphill battle. De La Cruz won reelection by 14 points in 2024, despite the Democratic Congressional Campaign Committee and other national groups targeting it as a potential pickup. The district leans Republican by a 7-point margin, according to the Cook Partisan Voting Index.

While Cuellar — who has no relation to Rep. Henry Cuellar, D-Laredo — is the first candidate to officially announce, Tejano music star Bobby Pulido has also been floated as a potential candidate. Pulido said he planned to enter politics in 2026, and he has been heavily recruited by Democrats, according to Politico.

Cuellar lives outside the district boundary, in the district of Rep. Vicente Gonzalez, D-McAllen. She is from Weslaco and went to college in Edinburg.

Members of Congress do not have to live in the district they represent, though residing outside the boundaries can open candidates to attacks from their opponents.

De La Cruz is the only Texas Republican the DCCC currently lists among its 2026 targets. But the spectre of redistricting, which could put more seats in play and upend the state’s political map, is hanging over both parties. South Texas is a key area where Republican map-drawers will likely try to draw friendlier seats by targeting De La Cruz’s Democratic neighbors, meaning the contours of the 15th District could change.

Under any new map, the district’s population is likely to remain overwhelmingly Hispanic — meaning Democrats will need to reverse their recent slide to have any chance of recapturing the seat.

Cuellar, a 43-year-old Rio Grande Valley native, believes Latino voters, in particular, were looking for change last cycle as they felt the bite of high costs fueled by inflation. She believes Democrats can position themselves as the party of change in 2026, especially on issues like health care, after Republicans including De La Cruz voted for Medicaid cuts as part of Trump’s recently enacted megabill.

“People are frustrated with health care costs, inflation, the economy, how difficult it is to succeed,” Cuellar said. “And I think a lot of frustrations were directed towards the Democratic Party.”

Democrats flipped the U.S. House in 2018 — including through pickups in Texas — largely by talking about Republicans’ efforts to quash the Affordable Care Act. Democrats hope to follow a similar playbook in 2026 by homing in on the Medicaid and ACA cuts in the megabill. Groups have been actively recruiting physicians like Cuellar to run for office as part of that pitch.

During her campaign, Cuellar said she also plans to discuss the need for a county hospital and more doctors in the district, along with plans to make health care more affordable.

Disclosure: Politico has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete list of them here.

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