Kogan and Wood’s paper provides a mechanism to explain that outcome. The authors found that increased coverage under Obamacare was generally associated with support for Democratic presidential candidate Hillary Clinton, holding all else equal. But things got more complicated when costs were considered, because as Kogan and Wood write, “premium increases moderated the political impact of exchange enrollment.” At both the county level and the individual-voter level, support for Trump was correlated with increases in premiums among people who self-purchased private plans—both on and off the exchanges—and those on Medicaid. There was not a similar correlation between support for Trump and premium increases among people with employer-sponsored plans.

In places where premiums rose for private-exchange plans, even the people who gained heavily subsidized or free coverage under the new law became more likely to support Trump.

Vladimir Kogan and Thomas Wood

Judging the candidates by their rhetoric, that would seem to make a certain degree of sense. Premiums skyrocketed in many exchange markets over 2015 and 2016, and one of Trump’s most frequent campaign promises was to reduce those premiums by repealing Obamacare.

But rising premiums on the exchanges did not mean that most Americans faced correspondingly large drains on their wallets. Those premiums only applied to people buying plans on the exchanges—the smallest piece of the insurance pie—and even then, some 85 percent of them received subsidies, shielding them from some or all of the increase in costs. That makes it hard to credit the notion that price pressures alone drove voters toward Trump.

The hypothesis put forward by Kogan and Wood is that overzealous and inaccurate coverage of premium increases by media outlets was largely responsible for boosting support for Trump. “Our results suggest that consumers were influenced not by the individual premiums they would have seen when logging in to renew their coverage,” they wrote, “but rather the coverage of the issue in the local press, which focused largely on the non-discounted rates.” The study doesn’t cite specific instances of such coverage. But when Aetna announced it would exit exchanges in 11 states in August of 2016, for example, much of the coverage focused on rising costs, often without specifying just whose premiums were increasing and how that actually affected costs for individual consumers.

If this hypothesis holds, it would confirm the fears of Kaiser Family Foundation president Drew Altman, who wrote in a July 2016 column in The Wall Street Journal that poor reporting about pre-discount premium increases led people to believe that their own out-of-pocket costs were increasing. “People may read news stories on premium increases as validating criticisms they have heard about the ACA,” Altman wrote. Eighty percent of the people in that month’s Kaiser Family Foundation tracking poll had seen reports on premium increases, and over two-thirds of those falsely believed that the increases applied to all plans or just to employer-based coverage. Poll respondents also consistently overestimated premium spikes, mistaking the highs reported for average increases, which in major cities hovered around 10 percent.