Few -- if any -- laws have divided the public like the Affordable Care Act. Ever since President Obama signed the federal health-care law four years ago this week, Republicans have pilloried it while Democrats have defended it.

But why do the law's supporters like it? And why do opponents hate it? Thanks to a poll released this week by the Kaiser Family Foundation, we can answer these questions.

The public remains more negative (46 percent hold an unfavorable view) than positive (38 percent hold a favorable view) toward the law, overall. That's the way it's been for much of the last four years.

Kaiser asked respondents open-ended questions about why they favor the law and why they don't. By far the most popular reason for supporting the law: Expanded access to medical care and coverage. Cost comes in second. The third most popular reason is that it's good for the country. Here's a chart, courtesy of Kaiser, that breaks it all down:

Opposition is driven by cost, distaste for the individual mandate, and a sense that the measure is an example of government overreach:

The fact that cost is an oft-cited reason why Americans like the law as well as a primary justification for why they dislike it speaks volumes for just how far apart the public is on the health-care debate. What one side sees as an attribute, the other side views as a problem.

Republicans and Democrats are already hitting on these themes in an effort to drive turnout in the November midterms. Republicans have been referencing Obamacare much more in the midterm campaign, given its unpopularity and troubled rollout. Expect to hear a lot more about government overreach and cost burdens from GOP candidates and groups.

Democrats have mostly adopted a keep-it-but-fix-it posture predicated on emphasizing the parts of Obamacare that are popular, like what it does to expand coverage, while underscoring efforts to fix the parts that are less popular.