About 11 percent of immigrants in the United States—five million—live in Texas. The state is home to an estimated 1.6 million undocumented persons—the second-most in the country after California. It is also led by Republican elected officials who are politically in lockstep with Trump.

When Trump left office in 2021, Gov. Greg Abbott surged resources to the state’s 1,254-mile border with Mexico through a border security mission, Operation Lone Star, that has so far cost $11 billion in state money. It includes the deployment of thousands of Department of Public Safety troopers and Texas National Guard troops to patrol the border. He started building a state-funded border wall after Biden ended Trump’s wall project. He sent busloads of newly-arrived migrants from border towns to northern cities led by Democrats.

Those state police and Texas soldiers could help Trump achieve his marquee campaign promise of launching mass deportations, according to immigration lawyers.

“We are in uncharted territory,” said Cesar Espinosa, the executive director of FIEL, an organization that offers education, social and legal services to immigrant families in the Houston region—home to about half a million people who are living in the country illegally.

FIEL—a Spanish acronym for Familias Inmigrantes y Estudiantes en la Lucha, which translates to Immigrant Families and Students in the Fight—tells their clients to prepare for “anything that can happen,” Espinosa said.

“We tell people that this is kind of like having a plan for a fire: You don't know if a fire is gonna happen, you can't predict when a fire’s happening, but you have a plan on how to exit,”Espinosa said.

On the campaign trail, Trump has called for a variety of measures that would significantly change immigration, asylum, and the lives of immigrants.

He’s said he will try to end automatic citizenship for children born to immigrants in the country. He’s suggested he would revoke legal status protections that the Biden administration has given to people from specific countries, like Haiti and Venezuela. He’s said he would re-implement policies from his first term, like ones that banned people from Muslim-majority countries and required asylum-seekers to wait in Mexico for the duration of their asylum cases.

But no proposal has received as much attention—or support from his fans—as Trump’s pitch to deport as many as 20 million people he’s said are undocumented. It is unclear how many undocumented people are in the country.

The last time the U.S. government undertook such a massive effort was in the 1950s during the Eisenhower administration, whose plan of pairing federal authorities with local police Trump has pointed to as a model for his ambitions.

“When there are state-level law enforcement officers and policymakers who support those initiatives, we might see an immigration enforcement authority that is far larger than Immigration and Customs Enforcement alone,” said Elora Mukherjee, director of Columbia Law School’s Immigrants’ Rights Clinic.

Texas, having deployed police and military for immigration enforcement on its own accord, fits the bill better than any state. While the Biden administration tried checking Texas’ authority—most notably suing to stop a new law that would let state police arrest suspected undocumented persons for illegal entry into the country—Trump has signaled he is eager to work with the state.

“When I’m president, instead of trying to send Texas a restraining order, I will send them reinforcements,” Trump told a crowd in Las Vegas in January. “Instead of fighting border states, I will use every resource tool and authority of the U.S. president to defend the United States of America from this horrible invasion that is taking place right now.”

Immigration lawyers say for Trump to accomplish his deportation promises, he could also rely on existing law enforcement agreements between federal and local authorities while expanding the use of “expedited removal,” a fast-track removal process that does not involve a person having to go before an immigration court.

Plus, he’s inheriting a ramping up of the nation’s deportation system that happened in the final year of Biden’s administration, said Kathleen Bush-Joseph, an analyst at the nonpartisan Migration Policy Institute.

From May 2023 through March 2024 alone, the Biden administration processed more migrants through expedited removal—316,000—than in any prior full fiscal year, according to a paper Bush-Joseph co-authored. The administration is on track to deport more people than Trump’s administration did in its first four years.

“My guess—I think it's a rational guess—is that there is going to be a lot of cooperation and synthesis between the state of Texas and the federal government,” said Joshua Treviño of the Texas Public Policy Foundation, a conservative think tank in Austin. “I don't think that Texas is gonna say, ‘Okay, it's done. I'm gonna wrap up Operation Lone Star.”

Abbott’s office did not respond to an interview request. He’s previously said the state will continue its border clampdown until there is a president in the White House who enforces immigration law. He’s also said the state won't stop its efforts until it has control of the border.

“The people who are in charge of bringing people across the border illegally are the drug cartels. The drug cartels haven’t closed out business, they haven’t gone away,” Abbott said in May in Eagle Pass. “We cannot relent in our security of the border.”

On Wednesday, Abbott told reporters that Trump will need time to bolster federal immigration enforcement and implement his border reforms, during which Texas must serve as a “stopgap.” He added that Texas “will have the opportunity to consider” repurposing Operation Lone Star money once Trump’s policies are in place.

Trump’s promised policies have the potential to upend the lives of millions in the state—as well as some big industries that rely on immigrant and migrant labor.

Immigrants account for roughly 18 percent of Texas’ population, but make up 40 percent of all employees in construction and a significant portion of workers in the oil and gas and mining industries, according to research papers published in September by the American Immigration Council, a Washington, D.C., group that advocates for immigrants.

“The impact that it could have on Texas could be monumental,” said Espinosa, of FIEL in Houston. “This could devastate a lot of industries here in Texas.”