Bill Gardner reviews research on the question:

Jon Krosnick, Wendy Gross, and colleagues at Stanford and Kaiser ran large surveys to measure public understanding of the ACA and how it was associated with approval of the law. They found that accurate knowledge about what’s in the bill varied with party identification: Democrats understood the most and liked the law the most, independents less, and Republicans understood still less and liked the law the least. However, attitudes were not just tribal. Within each party, the more accurate your knowledge of the law, the more you liked it.

Krosnick and colleagues found that most people favor most of the elements of the ACA, but not everyone recognized that these elements were all in the plan. Many people also have false beliefs about the plan. For example, only 42% of Americans correctly understood that the law does not provide free treatment for illegal aliens. Only 21% of Americans approve of this imaginary feature of the plan. This suggests that if the public understood the ACA perfectly, support for the law would be higher. Based on their model for how knowledge about the ACA is associated with approval for the law, Krosnick and colleagues project that in the unlikely case in which the public had perfect understanding of the law, the proportion of Americans who favor the bill might increase from the current level of 32% to 70%. Keep in mind, however, that Krosnick’s survey can’t show us that change in knowledge would cause change in approval. Perhaps causality runs the other way and it is approval of the law that drives people to seek information about what is in it.

But all of this is a huge indictment of the president’s and the Democrats’ approach to talking about the law. In my view, they should have been using every single opportunity to explain what the law actually does, compared with the system it replaced. Yes, there has been a mountain of propaganda against it. But that doesn’t excuse political malpractice in defending it. This is the Democrats’ most significant piece of domestic legislation in decades. And yet they cannot manage to make the case for it. That tells you so much about why that party remains such a shit-show, rescued temporarily by this president, but still wallowing in its own dysfunction, inability to communicate and pusillanimity.