In the election of 2010, the year of the Tea Party, Republican candidates for the House of Representatives won sixty-three seats that had previously been held by Democrats. This was the largest gain the Party had made since 1938, the year of New Deal weariness. The rout had a geographic dimension, giving Republicans new territory to govern. A third of the new seats came from four states: New York, Pennsylvania, Ohio, and Illinois. The new territory was heavily concentrated in older industrial towns. These areas were once thought of as union country, then they seemed emblematic of the Tea Party; now, as much as any place does, they belong to Donald Trump.

The changing geography of the conservative grass roots gives some clues about why the Party has been so receptive not just to Trump’s candidacy but to his message, an almost out-of-time economic nationalism. One reason that Trump’s campaign was so broadly ridiculed when it launched was that he could not seem to shake the concerns of the time when he first became a national figure. His campaign, with its loud talk of tariffs and foreigners ripping us off, seemed steeped in the “Red Dawn” sensibility of the mid-nineteen-eighties. The Trans-Pacific Partnership would be a “disaster,” Trump said. He could sound obsessed with, of all nations, Japan. “When was the last time you saw a Chevrolet in Tokyo?” he asked in the speech that launched his campaign. “It doesn’t exist, folks. They beat us all the time.” This of a country that has spent most of the new millennium in a deep economic malaise. But if Trump picked a strange example, it now seems that he picked the right anxiety.

Political scientists have found that if you know a single position that a voter holds (on abortion, for instance, or gun control) you can with great reliability predict the rest of his or her views. Polarization is that powerful a force. Trade, that atavistic issue, is an exception. As Alan Abramowitz of Emory University, among others, has demonstrated, when you know a voter’s position on one other issue, guessing his or her position on trade is essentially a coin flip. This idiosyncrasy persists in public-opinion surveys. The Pew Foundation sent me the results of surveys dating back to 1997 in which they asked about trade, and there is little consistent difference between the opinions of Republicans and Democrats. Interestingly, both groups tend to respond to the changing economic climate in the same way, their views of trade fluctuating together. But the ambivalence of Republican voters has not had much influence on how their representatives have voted: in Congress, Democrats have been mixed on trade deals (supporting some and not others) while Republican support has been close to unanimous. According to Jeffrey Kucik, a political scientist at the City College of New York, more than ninety-one per cent of Republican votes were cast in favor of every single trade deal between 2001 and 2014.

If the Pew data is right, then the ambivalence about trade among Republican voters has not changed much since 2010. But the support for free trade among influential leaders of the Party and the conservative movement no longer seems so uniform. This summer, more than fifty Republicans opposed giving President Obama the fast-track authority to close the Trans-Pacific Partnership deal, the first major trade vote in the Tea Party era. “I don’t like the idea of ceding American jobs,” Duncan Hunter, the right-wing California Republican, who is now one of two sitting congressmen to endorse Trump, said. “It’s all about favors for their buddies,” a spokesman for one of the leading Tea Party groups told Slate, explaining his group's opposition. Viewed from a certain angle, you could detect a political transformation in motion. The Republican Party, Kucik’s colleague and collaborator Daniel DiSalvo told me, has inherited not only some of the white working-class voters who have been abandoning the Democrats but also some of their economic nationalism.

It is hard to imagine that Trump saw this coming — that through the past half decade he was diligently tallying congressional votes, in his oversized scrawl, or filing away quotes from Tea Party notables skeptical about free trade. But the shift in the conservative movement on trade does seem like one suggestion that Trump does not represent an insurgency from outside the Party but an evolution within it—that some rough version of Trumpism already existed, and was part of how some Republicans were meeting a new demographic of voters.