Her father, Soukanh, fears what President Trump and his allies might do next on immigration. After more than two decades in the country, his wife is still a permanent resident, not a citizen, and is terrified of not being able to return to the country if she travels abroad. He is determined to vote for Democrats in the fall.

“Immigrants like us, we don’t feel safe,” Mr. Saignaphone, 63, said, with his daughter translating. “We’re citizens, but things can still happen to us. What if tomorrow he chooses our group to target?”

As they cast ballots in the primary last week, several voters in Aurora said that immigration was just as important an issue to them as rising health care costs and their struggles with soaring housing costs and student debt. Some had brothers and sisters who were protected under the DACA program; others had parents who had once been undocumented.

Luis Xoy, 47, who fled Guatemala in 1999, became an American citizen in January and voted for the first time in the primary. He criticized Mr. Coffman, saying the congressman paid lip service to immigrants but had not been able to pass any major reforms. Come November, he said, he will vote against Mr. Trump and other administration officials who “don’t think we’re human beings.”