Activists on the right said they felt betrayed by the Republicans they helped elect, who pledged that when they had a Republican president they would repeal the act “root and branch,” as Senator Mitch McConnell, the majority leader, once declared.

“This is not anywhere close to that, and I think it has left a number of conservative activists saying I’m not advocating for this,” said David Bozell, the president of ForAmerica, an organization founded in 2010, the year the Affordable Care Act was passed, to help spread conservative ideas on social media.

These activists want the subsidies that help people buy insurance repealed, not just reduced. They want the Medicaid expansion eliminated, not slowed.

“You’re not going to get a grass-roots activist to spend their valuable time calling their senator because, ‘Well, this is better than nothing,’” Mr. Bozell said.