MIAMI — Sylvia Maltzman, a part-time tutor at a community college in Florida, pays $23 a month for the health insurance she got under the Affordable Care Act. A federal subsidy of about $475 covers the rest, and Ms. Maltzman, who has high blood pressure and arthritis, said she could not afford insurance without it.

So she is prepared to demand that her elected officials, most of them Republicans, do something to help if the Supreme Court rules that people here and in other states that use the federal government’s insurance marketplace cannot receive subsidies. “I would hunt them down, and I would definitely let them know this could very well be fatal for me,” said Ms. Maltzman, 56, a registered Democrat.

Steven Brizuela, a Republican who lives not far from Ms. Maltzman in Miami, sees things differently. Mr. Brizuela, 20, who works at a clothing store and goes to college part time, said he had signed up for health care mostly because the law mandated it. Though he receives a subsidy of about $90 a month, he said he would rather have no insurance because he is healthy and finds his portion of the monthly premium, $45, a burden.

“I’m not going to take it out on them” if the subsidies are struck down, he said, referring to both political parties.