In California, an undocumented child can see a pediatrician, pay in-state tuition at public universities and receive state-funded scholarships. Immigrant farmworkers can likewise receive state-funded medical and dental care.

California leaders have gradually expanded the services available to undocumented immigrants, expressing a sense of obligation to workers who toiled in fields and factories and contributed to the state’s prosperity.

Other Democratic-led states have done the same, with growing confidence that they were free from federal interference as long as they paid for the benefits themselves.

But President Trump and congressional Republicans are now using various levers to upend those efforts from Washington. And Democrats, including three possible presidential candidates who have proposed scaling back immigrant benefits for their own reasons, are left wrestling with how to respond.

Republicans are driven, some of them say, by a belief that benefits for immigrants entice people to enter the country illegally. Other Republicans also say they object to the idea that Americans’ tax dollars — no matter where they are collected — go toward undocumented immigrants.

“They can just come in here and sign up for health care, and we’re supposed to pay for it at the expense of some of our most vulnerable citizens?” said James Gallagher, the Republican leader of the California State Assembly. “I don’t think that’s a right use of our priorities.”