The health care legislation proposed by Senate Republicans is a moral abomination—one that leadership is trying to pass through undemocratic means. Some of the villains responsible for this are obvious, starting with Donald Trump, Paul Ryan, and Mitch McConnell. But one conservative who played a major role in making the passage of an awful, widely despised bill frighteningly likely is flying under the radar: the chief justice of the Supreme Court.

John Roberts received a lot of praise from liberals for casting the swing vote in 2012 to mostly uphold the Affordable Care Act. But his decision in the case NFIB v. Sebelius to ham-handedly re-write the ACA’s Medicaid expansion denied a lot of people health insurance, made the Republican demolition of Medicaid more likely, and ensured that the death and suffering caused by TrumpCare will be harder, perhaps impossible, to fix.

It’s not just Roberts, of course. Seven justices voted to hold that Obamacare’s Medicaid expansion was optional for states, rather than a requirement to receive existing Medicaid funds. The Court’s five Republican nominees were joined by Obama nominee Elana Kagan and Clinton nominee Stephen Breyer. I think it’s overwhelmingly likely that the votes of Kagan and Breyer were strategic gestures intended to solidify Roberts’s decision to vote to uphold the ACA (after, apparently, initially voting to strike it down entirely). But it doesn’t matter—whether Kagan and Breyer voted sincerely or not, this holding is one of the very worst handed down by the Roberts Court, and it changed the political dynamics surrounding health care in critical ways.

The direct consequences of the decision were bad enough. Nineteen states still haven’t taken the Medicaid expansion, with the result that millions of poor, disabled, and/or elderly people are being denied insurance. But the indirect effects have also been very bad. The utter decimation of Medicaid is at the core of TrumpCare (it is even worse in the Senate version than in the House one). This would have been a lot harder to pull off if those 19 holdouts—all of them Republican-controlled—had taken the expansion money.

A new study shows that when a state took the Medicaid expansion, its residents became more likely to support the ACA. It would be more difficult to wreck Medicaid if more Republican voters had benefitted from the expansion. As the policy analyst Sean McElwee acidly put it, “The Republican Party’s strategic choice to brutalize their own voters by denying them health care basically worked.”