A Tea Party member reaches for a pamphlet titled "The Impact of Obamacare," at a "Food for Free Minds Tea Party Rally" in Littleton, N.H., on Oct. 27, 2012. (REUTERS/Jessica Rinaldi//Files)

On Tuesday, Hillary Clinton issued her defense of the Affordable Care Act and proposals to change the landmark health law, signaling the next battle in a war with all the signs of a political stalemate. Americans are basically evenly split in their assessments of the law and sharply divided along partisan lines; Republican presidential candidates want to scrap the law, while Democrats support keeping it (Clinton) or expanding it (Bernie Sanders). None of this is new to anybody, nor expected to change anytime soon.

But that conclusion misses a huge part of the story, according to just-published research by Johns Hopkins University sociologists. Stephen L. Morgan and Minhyoung Kang found the ACA's passage caused a sharp drop in support for health-care spending across party lines and might have ushered in a broader conservative "cold front" when it comes to other issues.

The chart below shows their core finding from the long-running General Social Survey. The percentage of Americans saying the country spends "too little" on health dropped from the years before and after its passage (comparing surveys from 2004-2008 to 2010-2014*). The falloff in support for greater health spending was sharpest among Republicans (24 percentage points), but was also large among independents (16 points) and Democrats (12 points).


Original chart annotated by Morgan & Kang, annotated by Washington Post.

Now, you might point out that support for health spending before and after Obamacare does not demonstrate that the law caused it to drop. The public could be reacting to something else, such as the stimulus policies enacted after the Great Recession or to government spending more generally.

But much of the authors' article in Sociological Science tries to rule out alternate theories. Running against the theory of a general backlash against federal spending, the drop in support for more health spending was much larger than it was in other areas, such as the environment or assistance to the poor. The cross-partisan drop in support also undermines the idea that support for health spending simply became more polarized along party lines, as many Democrats became less supportive of health spending after its passage. The authors found the over-time shift was similar even after controlling for demographics and political ideology and when looking at answers from the same respondents who were re-interviewed before and after the ACA.

In short, it's possible something else caused the drop, but Obamacare is the biggest culprit. The big question then is why support for health spending plummeted in reaction to the law. The researchers have some theories.

"The leading explanation is that the campaign to discredit the bill took a toll on everyone," Morgan said in a telephone interview. He and Kang argue that the ACA's passage might have ushered in a conservative "cold front," in which the public reacts to a pattern of growing liberalism by taking a conservative turn. Along those lines, the GSS survey found a smaller down-tick in support for national spending on a variety of issues beyond health care (including Social Security, assistance to the poor and help to other countries). The "cold front" idea was first proposed in the 1970s, when the public took a conservative turn on spending priorities after a long run trending toward liberalization.

A related theory is that public opinion is a thermostat. Morgan described it broadly: "As government expands, people become less enthusiastic about government expanding." Here's how University of Texas's Christopher Wlezien described it in a 1995 paper:

We observe that the signals the public sends to policymakers, in the form of preferences for “more” or “less” spending, react to changes in policy. ... [T]here is negative feedback of spending decisions on the public’s relative preferences, whereby the public adjusts its preferences for more spending downward when appropriations increase, and vice versa.

What's striking is that with the ACA, even Democrats behaved like thermostats, withdrawing support for increased health spending after the Democratic-sponsored law was passed.

The latest findings bolster the idea that, while most Americans do not want to repeal the law, Democrats paid a political price for passing the ACA. A 2012 political science article by Brendan Nyhan and colleagues estimated that Democrats would have retained at least 25 additional U.S. House seats in the 2010 elections if they had voted against the ACA, enough to maintain a majority. The cause? Democrats' votes in favor of the law led voters to perceive a member as being more liberal and distant, which was associated with lower support.

The evidence of a lasting public retrenchment on health care makes Democratic plans to protect or expand the law more politically challenging. Clinton introduced a cap on prescription drug prices at a rally Monday, saying, “I'm not going to let them rip away the progress we've made. I'm not going to let them tear up that law, kick 16 million people off their health coverage, and force this country to start the health-care debate all over again." Sanders doubled down on expanding health coverage, reiterating his support for a single-payer health care system this summer.

Democrats can take comfort that many of their specific policy proposals are popular. Indeed, the GSS found a majority of Americans and independents still says the country spends "too little" on heath.

But the bigger lesson is Americans tend to turn in the opposite direction of policy; Democrats won big in passing health-care reform, but the public's appetite for more ambitious action has shrunk.

Anne Gearan contributed to this post.