Brought to the United States from Venezuela as a toddler, Carlos Roa was among the first young undocumented immigrants to be protected from deportation under a program President Obama set up in 2012 by executive action.
Since then Mr. Roa, now 29, has put himself through college and is training to be an architect, drafting blueprints at a Chicago firm.
But with the election of Donald J. Trump as president, Mr. Roa and 750,000 other immigrants in the program, who came to the United States as children, have been swept up in a wave of anxiety, worried about losing the progress they have made and being forced back underground or even deported. Mr. Trump has promised to “immediately terminate” Mr. Obama’s executive actions on immigration, including the youth initiative.
“I have been here for 27 years, and I am not going anywhere,” Mr. Roa said, in between strategy sessions at Casa Michoacán, a gathering place in Chicago where immigrants planned moves to resist.
Young immigrants, who call themselves Dreamers, are already protesting at many colleges, and they have called for a march from New York to Washington starting Tuesday. They are pressing universities and employers to organize to defend the program and are making plans for havens on campuses and in churches.
Canceling the program is one move Mr. Trump could make to satisfy his supporters, who reject Mr. Obama’s executive actions as illegal amnesties and examples of presidential overreach. A larger program for undocumented parents of American citizens and legal residents was halted this year by the Supreme Court.
Most young people in the program are Latinos, and Latino organizations place a priority on protecting them, said Daniel Garza, the president of the Libre Initiative, a conservative Latino advocacy organization.
“These kids are going to be exposed if DACA is rescinded and that’s so unfair,” Mr. Garza said. “We should be keeping families together, not tearing them apart.”
Mr. Trump has not provided details of his plans and his transition team did not respond to emails requesting comment.
But the program was set up through policy guidelines written by the secretary of Homeland Security at the time, Janet Napolitano — there is not even a formal presidential order — so it can be terminated with a stroke of a new secretary’s pen.
Immigrants are taking Mr. Trump at his word when he said he would eliminate the program: He has selected Senator Jeff Sessions of Alabama, a Republican who is one of its most vigorous opponents, as attorney general.
Another Trump adviser, Kris Kobach, the Republican secretary of state of Kansas, brought a federal lawsuit against the program in 2012; it did not succeed.
Mr. Trump’s pledges are chilling for the immigrants because when they signed up to the program, they provided identity information — including the names of their parents, home addresses, utility bills and school transcripts — to United States Citizenship and Immigration Services. The authorities deferred any action to deport them and gave them two-year renewable work permits, but no official immigration status.
Administration officials said the citizenship agency could be asked to turn over that information to Homeland Security enforcement agents, who could track down the immigrants to deport them or their parents.
Mr. Trump could also take a less harsh approach by allowing existing work permits to lapse and not approving new ones, but not initiating deportations.
Advocacy groups have been inundated with calls from people afraid or despondent.
Ruben Rivas, 27, a Mexican immigrant, said he had vacillated from fear to sadness to denial. In 2012 Mr. Rivas, the son of undocumented immigrants who spent their lives working minimum-wage jobs, graduated from San Jose State University with a degree in business finance.
He applied that year for DACA, never stopping to worry about offering the government details about his life. Now he works as a financial consultant and co-owns a small income tax firm.
“The first thought I had is that I have done everything right and it is all going to be taken away from me,” he said of his fears for the future of the program. “It feels a little bit like a betrayal. I’ve been here since I was 4 years old. I’m an American.”
Jennifer Marin, 29, a legal assistant, was brought to California from Guatemala when she was 1 year old. As a student at California State University, Dominguez Hills, she worked at a check-cashing store to pay her tuition. She applied for the program to get her driver’s license, worried that one missed stop sign could send her to jail and deportation, a prospect she could not face with two children.
Now she has a license, a car and a home in a Los Angeles suburb she bought with her savings.
“It feels like a step backward, to be back in this insecure place where you don’t know what the next step might be,” she said, her voice breaking with tears. She has tried not to cry in front of her children and to assure them that she is safe.
Last week, Mr. Obama appealed to Mr. Trump “to think long and hard” before scrapping the program.
Dick Durbin of Illinois, the second-highest Senate Democrat, said on the floor and on Twitter that he would do “everything in my power” to save the program and protect “Dreamers who have stepped forward to contribute” to the country.
Rights groups have been encouraging immigrants up for renewal on the program to reapply quickly. But they are generally urging newcomers not to apply.
“The risk for everyone feels much larger than the potential benefit right now,” said Daniel Sharp, the legal director of the Central American Resource Center, a nonprofit legal aid organization in Los Angeles. Groups are pressing the Obama administration to speed up approvals to eliminate any backlogs before Mr. Trump takes office.
On Thursday three House Democrats, including Representative Luis V. Gutiérrez of Illinois, asked Mr. Obama to issue a pardon to immigrants in the program. But White House officials said the president did not have the authority for a pardon that would provide lasting protection.
If their work permits are canceled or expire, immigrants could face cascading consequences — losing jobs, driver’s licenses, professional certificates and the chance to pay in-state tuition for college. The impact would vary by state. In places like California — home to half of all DACA recipients — and New York, additional protections are enshrined in laws. But in the South and Midwest where there are fewer protections, “people might find they really stand out and are targeted,” said Roberto Gonzales, a Harvard professor who has studied young people in the program.
Yet there were signs that young immigrants, who have been battling for a legal foothold in the United States for more than a decade, would not go back underground quietly.
United We Dream, a national organization of young immigrants, said it would work with Voto Latino, a voter mobilization group, to encourage colleges to create havens for students who become undocumented once again. At the University of Houston, students organized a walkout on Monday and are working with local activists to designate the city as a sanctuary for undocumented immigrants.
Mr. Roa, in Chicago, recalled that a decade ago he was afraid to confess his undocumented status to other students or have his photograph published in a newspaper.
“Do you really think we are going back in time?” he asked. “I am going to be kicking and screaming.”