A sizable minority of Americans don’t understand that Obamacare is just another name for the Affordable Care Act.

This finding, from a poll by Morning Consult, illustrates the extent of public confusion over a health law that President Trump and Republicans in Congress hope to repeal.

In the survey, 35 percent of respondents said either they thought Obamacare and the Affordable Care Act were different policies (17 percent) or didn’t know if they were the same or different (18 percent). This confusion was more pronounced among people 18 to 29 and those who earn less than $50,000 — two groups that could be significantly affected by repeal.

Among Republicans, a higher percentage (72 percent) said they knew Obamacare and the A.C.A. were the same, which may reflect the party’s longstanding hostility to the law.