There were times when even Sullivan—who, despite his gravitas, occasionally dips into Midwestern aw-shucksisms—couldn’t believe the life he was living. His first time in the Situation Room, he has said, he felt like there had to be “another room down the hall” where the real decisions got made. “And then you realize there isn’t another room,” he said. “There’s only us.”

During the Obama years, Sullivan was known for his upbeat and even disposition—at a going-away party for him at State, he was tagged with the moniker “Mr. Sunshine.” He had an almost Socratic approach to navigating disagreements. Without ever raising his voice, he would turn over counterarguments until every logical flaw had been exposed and probe his sparring partners with respectful but incisive questions.

Jennifer Harris, then a policy planner at State, said she would often share with Sullivan what were, at the time, “heretical” views about free trade and globalization. For decades, the mainstream policy wonks had said it was best for governments to take a hands-off approach to global trade—let the invisible hand balance the scales. But Harris was watching China hollow out US industries by plowing money and stolen American IP into homegrown competitors. The US government, Harris argued, needed to hit back.

Sullivan was one of the few people in the administration who would actually hear her out. Then, Harris recalled, he’d ask her for reading assignments. “He really worries about blind spots,” she said.

But if Sullivan was open to rethinking free trade, he hadn’t yet fully embraced Harris’ arguments. When Clinton ran for president in the 2016 election, Sullivan joined her on the campaign trail, talking up the merits of the “liberal international order” and open markets. Pundits predicted he would become the youngest national security adviser in history when Clinton took office. But voters had a different plan. The morning after Trump’s victory, looking drawn and despondent, Sullivan sat between Robby Mook, Clinton’s campaign manager, and Huma Abedin, her closest aide, as Clinton delivered her concession speech.

Sullivan balks at the suggestion that the Trump years were some period of soul-searching for him (“that’s pretty existential for an Irish guy”), but he did process Clinton’s loss in his own way. From a new perch at the Carnegie Endowment for International Peace—one of many hats he wore during this time—he researched, conducted interviews, and wrote extensively. Sullivan came to realize that he’d had a blind spot—a big one. Somewhere along the line, he and the rest of the Washington foreign policy establishment had failed to effectively make the case for how decades of globalism benefited the average American. Perhaps worse, they’d failed to really grapple with the ways in which it didn’t benefit regular people at all. Donald Trump had made that case, however sloppily.

Sullivan’s blind spot wasn’t just about economics. While the US was shipping jobs and industries overseas, it was also providing China open access to sensitive technologies. It didn’t take a Rhodes scholar to see the problem. “If you ask someone where I grew up, ‘Hey, do you think we should give computer chips for use in Chinese nuclear weapons?’ They will be like, ‘No,’” Sullivan told me. “Somehow, we missed out on the common sense proposition.”

By the time he joined Biden’s campaign for president in 2020, Sullivan believed securing the United States’ lead in emerging technologies was the clearest path to creating American jobs and fending off China’s competitive threat. As it turned out, it was also good politics.