LAREDO, Texas — Two years ago, a 26-year-old immigration lawyer named Jessica Cisneros came within 3.6 percentage points of pushing out the longtime Democratic congressman here, running aggressively on the progressive vision of the national liberals who had bankrolled her insurgent campaign.This time around, at the ripe age of 28, she’s scorching the already brown earth of South Texas, attacking Representative Henry Cuellar not so much for his conservative policy positions, but for being what she describes as a corrupt politician — rich, out of touch with his poor constituents, and quite possibly a felon.“We’re going after him,” Ms. Cisneros said at a picnic table outside the taqueria next to her campaign headquarters, with the confidence of a seasoned political street fighter. “Everything we’ve been doing has been very intentional.”Texas will kick off the 2022 primary season on Tuesday, launching what promises to be a grueling series of contests that could pull both Democrats and Republicans toward their political extremes, while testing the grips that President Biden and former President Donald J. Trump have over their respective parties.In South Texas, another test is developing over the power of identity politics and whether liberals can answer the fears that conservatives are stoking about “open borders,” “critical race theory” and rising crime. In the primary campaign for Texas’ 28th district, it is Mr. Cuellar’s experience versus Ms. Cisneros’s storytelling: the powerful and connected versus the underdogs, the community, the “pueblo.”There have been many changes here since Ms. Cisneros first challenged Mr. Cuellar, but the most significant may have been the shock for both parties of seeing Hispanic voters lurch toward Mr. Trump in 2020. Zapata County, just south of here, is heavily Latino; Hillary Clinton won it by more than 30 points in 2016, then it went to Mr. Trump by about five points. Ms. Clinton’s 60-point margin in Starr County, which is 96 percent Latino, shriveled to a five-point advantage for Mr. Biden.In response, Ms. Cisneros is running a campaign against the 17-year incumbent that could easily have been engineered by a Republican. She still favors Medicare for All, a $15 minimum wage, more liberal immigration policies and abortion rights, but those have not been her focus.Instead, she has played up her biography and hit Mr. Cuellar hard on rising prices. She has portrayed him as a Washington insider, greasing his pockets with money from big corporations, and presented herself as embodying the struggling community he left behind.“My medicines cost more, insurance more,” intones an older Latina in one of Ms. Cisneros’s most recent ads, as the woman sweeps the stoop of her modest house and laments that nothing has changed in Laredo. “Now it’s food and gas, but we don’t make more. If you ask me, Henry Cuellar has been in Washington too long.”The mysterious raid last month by the F.B.I. of Mr. Cuellar’s Laredo home and campaign office presented a late, potentially devastating twist that seemed to confirm all that Ms. Cisneros had been saying of the congressman — and she pounced on it.Senator Elizabeth Warren of Massachusetts, a fellow progressive, campaigned recently for congressional candidate Jessica Cisneros in San Antonio.Ilana Panich-Linsman for The New York TimesJustice Democrats, the progressive insurgent group that has greatly bolstered her campaign, has piled on with a decidedly nonideological advertisement blanketing South Texas that accuses Mr. Cuellar of hitching rides on donors’ private jets, fixing his BMW with campaign cash and drawing that raid by the F.B.I.Progressives have been on a losing streak of late. In August, a hero of the left, Nina Turner, lost a special election in Cleveland to a candidate backed by establishment Democrats. Representative Marie Newman of Illinois, who in 2020 defeated one of the last House Democrats who opposed abortion, is under an ethics investigation, accused of enticing a primary rival out of the race two years ago with a promised job in her congressional office. Democratic leaders have struggled to distance themselves from the sloganeering of “Defund the police,” while Republicans have demonized progressive views on race and gender.A Guide to the 2022 U.S. Midterm ElectionsIn the Senate: Democrats have a razor-thin margin that could be upended with a single loss. Here are the four incumbents most at risk.In the House: Republicans and Democrats are seeking to gain an edge through redistricting and gerrymandering.Governors’ Races: Georgia’s contest will be at the center of the political universe, but there are several important races across the country.Key Issues: Inflation, the pandemic, abortion and voting rights are expected to be among this election cycle’s defining topics.Like Ms. Cisneros, liberal organizations are trying to adjust.“We are definitely aware of the Trump swing,” said Waleed Shahid, a spokesman and strategist for Justice Democrats, which helped Alexandria Ocasio-Cortez of New York, Cori Bush of Missouri and Ayanna S. Pressley of Massachusetts defeat veteran Democratic incumbents over the past four years.Mr. Cuellar and his supporters have greeted the onslaught with disbelief. The veteran Democrat may be the last in the House who opposes abortion, and he has taken a tougher line on immigration, border security and law enforcement than many of his colleagues. But that is not what the campaign seems to be about.“They really don’t talk much about what they want to do, except in general terms,” Mr. Cuellar said. Instead, he said, “it’s attack, attack, attack, attack, attack, attack.”He said in January in a video statement on Twitter that the ongoing investigation — which appears linked to a broader inquiry into the political influence of Azerbaijan — will show “no wrongdoing on my part.”Supporters of Ms. Cisneros — and some Democratic thinkers — see in her shift a model for the party in the Trump era of personal politics. Republicans, and to some extent Mr. Cuellar, have created a frightening narrative that feels more urgent than any policy debates in Washington. That story contends that decent, hard-working people are playing by the rules, but strangers are pounding at the door, and neighbors are grabbing all they can from the government.Ian Haney López, a public law professor at the University of California, Berkeley, who has studied the Hispanic shift in South Texas, said Ms. Cisneros is using identity to try to galvanize support without alienating the white voters who remain the majority nationwide — though not in the 28th district of Texas.Since the rise of Trumpism, with its appeals to white grievance and fears, he said, Democrats have taken two approaches, both of which have failed. The progressive wing has called out Mr. Trump and his supporters as racist, and urged voters to band together to fight white racism.“That identity story casts the majority of Democratic voters as part of the problem,” he said. In addition, 2020 proved that tactic was also not helpful to the Democratic cause with people of color, especially Latinos. “You’re not going to get them to sign on to a story that says you’re on the margins, you’re widely hated, and your children’s lives will be truncated by racism.”Jessica Cisneros hands out campaign flyers in Laredo, Texas. She is supported by the same progressive group that helped Alexandria Ocasio-Cortez of New York, Cori Bush of Missouri and Ayanna S. Pressley of Massachusetts defeat veteran Democratic incumbents.Ilana Panich-Linsman for The New York TimesMore centrist Democrats, recognizing the perils of that approach, have eschewed identity politics altogether and stuck with dry policy arguments — a strategy Mr. Lopez called “nonsense on stilts.”In Ms. Cisneros’s campaign, he sees an identity-first approach, in which she casually toggles between English and Spanish, speaks of identifying with South Texas and its struggles, contrasts that to the outsiders in Washington, then pivots to issues like health care and reproductive rights.After the Trump shake-up, the region could be ready for a new approach, said Cecilia Ballí, an anthropologist and researcher at the University of Houston who did extensive interviews in South Texas after Mr. Trump’s 2020 gains. For decades, the region has been run by insular political families like Mr. Cuellar’s. His brother is the sheriff of Laredo’s Webb County; his sister is a former municipal judge and tax collector there.Ms. Ballí said that with no real competition between the parties, Democrats have won loyalty with rallies and free food, but no emphasis on issues or retail politics. Mr. Trump’s brand of personality-driven, outsider bombast broke through to many disillusioned Hispanic voters.Ms. Cisneros agreed: “They’ve been voting Democrat for such a long time, and obviously, the poverty rate hasn’t gone down, the uninsurance rate hasn’t gone down. People still have to work two or three jobs just to make ends meet.” she said. Add the pandemic and a shutdown of border crossings that crippled Laredo commerce, “and I think that just led to the perfect storm.”Mr. Cuellar has weapons of his own: an unrivaled network of backers in the political establishment and a seat on the House Appropriations Committee, from which he has plied the sprawling district with federal largess, from $45,520,000 in transportation projects for Atascosa County in the district’s north to $15,142,000 for cattle health in Zapata County in the south.Then there are the fears that a Cisneros victory March 1 would hand newly confident Republicans the seat. Ms. Cisneros insists that she is the answer to the Republican rise, an outsider voice to give hope to the region’s frustrations. Redistricting changes actually made the 28th slightly more Democratic, with more voters from San Antonio’s Bexar County, a potential boon to Ms. Cisneros’s chances — on Tuesday and in November. The district shifted from 76.9 percent Hispanic to 75.3 percent, but a slight rise in Anglo voters could actually help Ms. Cisneros if those new voters are San Antonio liberals.But Mr. Cuellar beat his Republican challenger handily in 2020, with 58 percent of the vote, while Mr. Biden eked out 51.5 percent. Those Trump-Cuellar voters could move to the Republican House candidate that emerges from the seven-candidate primary.“If Henry loses, then they have won this seat,” Anna Cavazos Ramirez, a former Webb County attorney, said of the Republicans.The negative tone of Ms. Cisneros’s campaign has turned off some voters, who speculated that the raid last month — still unexplained — was somehow the work of her supporters. Pastor Tim Rowley, who ministers at one of Laredo’s largest evangelical congregations, Grace Bible Church, said the campaign had left him saddened.“Whether you’re Democrat or Republican, rather than getting up and fully debating the issues, it just seems to be a smear campaign,” he said, suggesting he would likely vote for Mr. Cuellar because “this has to stop.”Miguel Sanchez, 35, was not so quick to dismiss what he called “that incident,” when F.B.I. agents were seen carrying items from Mr. Cuellar’s Laredo home. Mr. Sanchez had come to a rally at Texas A&M International University for Beto O’Rourke, the Democrat running for Texas governor, but the longtime Cuellar supporter was giving the House primary a lot of thought.“Cisneros, she seems to be a breath of fresh air,” he said, adding, “It’s been a long time since we’ve had a grassroots-type Democrat.” As for the incumbent, Ms. Cisneros’s message has gotten through.“I don’t know,” Mr. Sanchez said, shaking his head. “We don’t need politicians like that in Washington.” More