Across the country, many Democrats have made the calculation that embracing the law offers more risk than reward.

The architecture of the law almost ensured this outcome. To win over centrist Democrats, the administration proposed a complicated, market-based overhaul that was undergirded politically by Mr. Obama’s promise that individuals could keep their existing health plans.

“It was sold as small, minor change because of the need to pass it through Congress and assure the vast majority of people that it wouldn’t disturb their existing health insurance,” said Stanley B. Greenberg, a Democratic pollster. “But why defend it, why mobilize behind it if it’s just small change?”…

“This is where the communications failure has been so problematic,” said Ezekiel J. Emanuel, one of the law’s architects. “We haven’t really alerted Americans to the fact that there is much more to this than the exchanges that’s going to be really, really positive for all of us, not just those getting insurance.”…

“In the ’60s, we felt like we could do anything,” recalled Joseph A. Califano Jr., a top domestic aide to Johnson. “We could feed the hungry, cure disease and clean the air. Now there’s just a lot more skepticism.”