Before Sen. Chuck Grassley took center stage as the new chairman of the Senate Judiciary Committee, leading the confirmation hearings on attorney general nominee Loretta Lynch, he cut his teeth grilling every member of the current Supreme Court.

The oldest of those hearings, in 1986, happened to involve a judge who would become the youngest sitting justice at the time, Antonin Scalia. Among other concerns, Grassley took the D.C. Circuit nominee to task over his views on legislative history, particularly the relevance of committee reports in the interpretation of statutes. Grassley seemed troubled by a case Scalia had decided that showed “hostility toward committee reports.”

Scalia replied, “Senator, Congress does not act in committee reports. I will say that flat out. Congress acts by passing a law.” All Scalia sought to do, he later expounded, was to not arrive at a conclusion about a meaning of a statute that didn’t represent “the whole body” of lawmakers—that judges “are not disenfranchising the Congress and getting you, as a member of the Senate, committed to a position which in fact you knew nothing about and would disagree with.”

Grassley wasn’t very sympathetic to that response, and in fact took umbrage at Scalia’s “lack of deference to the methods of the legislative branch.” He ended his line of questioning with a strange rant on how working in Congress might help him view legislative history with more respect.

Much of the recent debate about King v. Burwell, the pending challenge to the Affordable Care Act before the Supreme Court, has centered around precisely that issue: to what extent the court should defer to legislative history in reading the healthcare law. Does the intent of Congress matter in interpreting whether the law was written to make healthcare affordable for everyone? Was it written to provide federal subsidies for Americans in all 50 states, even those states that chose not set up healthcare exchanges?

Reasonable minds have spilled considerable ink on that debate. But very little of it, if any, will matter to Scalia. Both his answers to Grassley and his decades of jurisprudence point to the greater virtues of textualism—what the letter of the law actually says. His own 2012 treatise on interpreting statutes, Reading Law, is popping up in court decisions all over the country, including at the Supreme Court.And both the challengers and the federal government in King have been wise to make their central argument that the text of the healthcare law is clear and unequivocal. Their conclusions may be entirely different—they each argue for and against the provision of federal subsidies for people residing in states without healthcare exchanges—but they agree on the premise of the law’s clarity.

Textualism is that brutal. A law either provides for something or it doesn’t. Which is why litigators on both sides wrote their respective briefs as if aiming for Scalia’s favor. Both point to the “plain text” or the “plain meaning” of Obamacare early on in their arguments, burying or downplaying talk of legislative history for much later. That’s smart strategy. Scalia couldn’t possibly be convinced that the health law is constitutional—he would’ve gotten rid of the whole thing in 2012 when it first came before the court—let alone that the intent of Congress, or what a lone senator said or did, are the decisive factors. But he could very well be moved to uphold the statute under the theory he has championed since that fateful one-on-one with Grassley.

This explains why Abbe Gluck, a Yale law professor specializing in statutory interpretation, has written that King is “textualism’s big test”—if its invocation and proliferation over nearly three decades means anything, it must serve the goal of upholding the provision of subsidies to every state under the Affordable Care Act. In her view, every part of this interlocking statute, in the aggregate, compels such a reading, and to arrive at any other interpretation would simply do “violence” to a text duly enacted by Congress. And if such violence also means “corrupting” the legacy that Scalia has taken his entire judicial career to build, so be it.

But a glance at Scalia’s recent pronouncements on textualism suggest none of these extreme results. Take Utility Air Regulatory Group v. EPA, an environmental-law case where the justice wrote of the“fundamental canon of statutory construction that the words of a statute must be read in their context and with a view to their place in the overall statutory scheme.” The Obama administration lost in that case, but the loss was minor. “It bears mention that EPA is getting almost everything it wanted in this case,” Scalia said while announcing his opinion. At least when it comes to interpreting a statute, it seems that Scalia is less interested in the politics of interpreting a statute than how to interpret it.

Perhaps the greatest testament to Scalia’s consensus-building around textualism occurred in two cases decided back-to-back earlier this month. One case was criminal and the other one civil, but both involved unanimous rulings—sharp, crisp, and to the point—on how two distinct texts enacted by Congress compelled results benefitting loan borrowers and kidnapping victims. Neither case was nearly as complex as King, but both point to the greater theme of Scalia’s preference for finding harmony rather than dissonance in statutory text.

And just last week, in a closely watched case involving the Fair Housing Act, Scalia lectured a Texas attorney opposing the 1968 law that the court is obliged “to construe the plain text of the law” as a whole, including the original statute and later amendments to arrive at a proper interpretation of what it all means. This was a shock to many a journalist and commentator—the notion that a justice otherwise hostile to the constitutionality of civil rights laws may otherwise be inclined to uphold them if they’re adequately written.

Naturally, this is far from an exhaustive dossier on the court's greatest textualist. But taken together, these clues—plus those to come in the lead-up to the King ruling in June—point to Scalia as a decisive vote in whether federal subsidies for all Americans survive. Since no other justice or potential swing vote is nearly as committed as Scalia to the importance of textualism, it will take convincing him to save the law. Because if Obamacare crumbles, the house Scalia worked so hard to build could very well crumble with it, too.