Photo

CEDAR RAPIDS, Iowa — Making her final push before the Iowa caucuses, Hillary Clinton staked out her position as the lone defender of the Affordable Care Act on Saturday night, warning that her Democratic rival, Senator Bernie Sanders, would scrap it and start over and that Republicans would hand healthcare back to insurers and drug-makers.

While she tends to lump Republicans with Donald J. Trump these days, Mrs. Clinton made clear that she is also paying attention to Senator Ted Cruz.

The Texas senator found himself in an awkward position on Saturday afternoon when a supporter of Mrs. Clinton confronted him at a rally about his plan to repeal the Affordable Care Act.

The man told a painful story of how his brother-in-law was unable to get insurance before the law was passed and that when he finally could finally see a doctor, he learned that he was a riddled with cancer. After briefly expressing condolences, Mr. Cruz went on to assail the law.

The exchange caught Mrs. Clinton’s attention.

At a rally in a high school gymnasium where she was joined by her husband and daughter, Mrs. Clinton brought up the story as an example of why it would be dangerous to elect a Republican such as Mr. Cruz as president.

“Cruz went off on one of his ideological, critical comments about the Affordable Care Act,” Mrs. Clinton said after recounting the confrontation. “He never says what the alternative would be.”

Mrs. Clinton went on to say that Mr. Cruz and his Republican colleagues have no plan for replacing President Obama’s signature piece of legislation because they intend to leave health care in the hands of big companies.

“That’s fine for them,” she said. “It’s not fine for me.”

The future of the Affordable Care Act has been a hot subject for both Democrats and Republicans, as Mr. Sanders wants to replace the law with a government-run Medicare-for-all program. Mrs. Clinton has argued that while she, too, wants all Americans to be insured, Mr. Sanders’s plan could not pass. Re-igniting such a debate, she predicts, would be wrenching for the country.

“We can’t repeal it and we can’t start over,” Mrs. Clinton said.