WESLACO, Texas—Abad Morales, who owns a construction company here in South Texas, was swayed by President Trump’s 2024 campaign question: “Are you better off today than you were four years ago?”Two years later, he is asking himself the same question—and now, he says, life has only gotten worse.

Morales is having a harder time finding workers for his construction jobs and says the cost of everything continues to rise. His company won’t be able to host an annual toy drive this year because he has opted instead to use the money to help friends and local families who have been deported.

His frustration with Trump has pushed him deeper into politics. Once largely disengaged, Morales is now running for the city commission in Weslaco and has become a Democratic precinct chair. By his count, he has helped more than 350 voters this year.“I’m done. I don’t think it’s right what he’s doing at all,” Morales, 36 years old, said of Trump.

“We need a change. It’s time to put our foot down and make a change.”

As Texans head to the polls to decide some of the nation’s most closely watched races, Latino voters—who helped propel Trump’s return to the White House in 2024—once again could play a decisive role, this time in determining whether Democrats win majorities in the House and Senate. A recent Wall Street Journal poll found a majority of Latino voters picking a Democrat for Congress over a Republican, 53% to 35%. On Trump’s job approval among Latinos, only 26% approve while 68% disapprove—significantly lower than his approval of 37% with voters overall, the poll found.

In 2024, Trump flipped all four counties in the Rio Grande Valley, a predominantly Latino region that had long been a Democratic stronghold in Texas but had shifted rightward in recent elections. At the time, he appealed to Hispanic voters, especially men, with promises to lower the cost of living and tighten border security and immigration enforcement.

Now, signs of growing disenchantment with Trump over his handling of the economy and his administration’s immigration crackdown suggest the gains are unraveling. Early voting figures in Texas point to a surge in Hispanic voter turnout. As of Monday, the eighth day of the state’s two-week early voting period, turnout in the region was far ahead of the 2022 midterms. Statewide, Hispanic turnout was making up a higher share of the electorate compared with the same point in the 2022 and 2024 elections, according to an analysis by Texas consulting and analysis firm Ryan Data & Research.

Texas Republicans redrew the state’s congressional map last year in part around the gains they had made with Latino voters, betting on that support to flip five Democratic-held congressional seats. But several of those races are now competitive, meaning Republicans could fall short of their goal.

The region could also prove pivotal in the state’s marquee U.S. Senate race between Republican Ken Paxton and Democrat James Talarico.

The Talarico campaign made an early and forceful investment in courting Latino voters— including with major spending on Spanish-language ads—and they ultimately backed him strongly in the Democratic primary.

Talarico told the Journal that many Hispanic Texans put their faith in Trump because they thought he was going to lower costs, drain the swamp in Washington, D.C., bring an end to wars and release the Epstein files—and now think he hasn’t followed through. “A lot of Hispanic Texans are feeling disillusioned,” Talarico said. “They’re feeling like they were let down. And they’re looking for a senator who’s actually going to deliver on their promises.”

Republicans are still trying to appeal to Latinos, in part by casting Democrats as too liberal on social issues.

Trump, who has campaigned several times in Texas this month to boost Paxton, has said that he hasn’t lost Hispanic support.“We have to do what we have to do,” Trump said earlier this month of his immigration crackdown when asked his message to Hispanic voters who feel betrayed by his policies.

Anthony Acosta, the owner of two Mexican restaurants in the Rio Grande Valley, said he had seen a lot of competitors go out of business because costs keep rising and fewer people are going out to eat—either because they can’t afford it or they are scared of run-ins with immigration agents. Acosta, 34, has never voted in a federal election, feeling in the past that his vote didn’t count. But he is planning to vote this year. “I don’t play scratch-offs, but when things are really really bad, I’ll take whatever chance I can get. One in million, one in a billion,” Acosta said. “Hey, you know what? A little bit of hope is better than no hope at all.”

Conversations with voters, strategists and candidates signal, however, that while Latinos are moving back toward Democrats amid frustration with Trump, it doesn’t mean Latinos are back to being reliable Democratic voters.

At the state’s southern tip, advertising for Republican congressional hopeful Eric Flores looks normal at first: Red billboards feature a smiling photo of Flores alongside Trump. They declare “Trump Endorsed” at the top of the sign and “Support ICE!” at the bottom. But look closer and the signs disclose that that they are paid for by local Democrats—showing how much Democrats think Trump’s flagging approval ratings will hurt Republicans. Flores is challenging Democratic Rep. Vicente Gonzalez in one of the districts redrawn to help the GOP, a race the nonpartisan Cook Political Report recently changed from a tossup rating to leaning Democratic.

The Flores campaign sent a cease-and-desist letter to a billboard company seeking to have the signs, and others mimicking Flores signage, taken down.

“That’s what Democrats think will be damaging?”Flores said of his endorsement from Trump. “Why aren’t they running on their positive platform?”

Flores has been campaigning on his record as former Army National Guard infantry captain and federal prosecutor, saying the country needs to balance border security with a visa program for workers and focus on energy independence. But Gonzalez has sought to tie him to Trump-administration policies.WSJ’s Sabrina Rodriguez returns home to Miami, Florida, to see how the soaring cost of living and the current immigration crackdown are impacting voters’ opinions ahead of the midterms. Photo: WSJ / John McColgan“This gentleman has somehow painted me out that I’m responsible for the Iran war, for higher gas prices,” Flores said. “I’m not the elected official.”

David Garza, an attorney in Brownsville, has always supported Trump. He praised the president for getting the border under control. It was a welcome development for many in the region who had grown frustrated with the sustained influx of migrants and what they saw as a chaotic situation at the border. But he said he felt Trump had gone off track on several issues, including starting the war in Iran and with his immigration-enforcement tactics.A conservative Republican, Garza said he still likes Trump overall.

But when it comes to the midterms, he plans to leave at least three races blank on his ballot because he opposes the Republicans in those races and won’t back the Democrats. He wouldn’t say the candidates’ names aloud but said he wouldn’t vote for them because of “personality issues” and “too much baggage.”“There’s a few people like me that are going to sit it out,” he said. “I made up my mind.”

Contractor Benny Melendez voted for Trump in 2024, upset about inflation under the Biden administration and the border crisis he saw locally. Now, he said he regrets it, as he has watched his workers—even those with valid work permits—dragged from job sites.

He can’t get houses finished and this year will see no profit, he said.“I decided to punish Biden and the Democrats by voting Republican and now, for the same reason, I’m going to punish Trump and vote Democrat again,” Melendez said. “I’m tired of playing that game.”Write to Sabrina Rodriguez at sabrina.rodriguez@wsj.com and Elizabeth Findell at elizabeth.findell@wsj.com