As he weighed the decision with his wife, Cheryl, he made a point of soliciting advice from each of his five children. One of his sons was serving in a Mormon mission overseas, and unreachable by phone, so they corresponded via email. Another, his youngest, had spent the summer interning at the Capitol. He was just a year old when his dad was first elected to Congress. “In some sense, it’s about all they know,” Flake said of his kids. “They’ve followed politics enough to know what works and what doesn’t in a campaign.” When it came time to finalize his decision over the weekend, the family was unanimous: “To a person, everybody realized … that to win the primary I would have to run a campaign that I would not be comfortable with, and that I wouldn’t be proud of. And they didn’t want me to do that.”

By the time we spoke on Tuesday night, the initial round of praise for his Senate speech had already begun to give way to a chorus of critics, like the New York Times columnist Ross Douthat, who dismissed Flake’s “surrender” as embodying “the not-quite-admirable courage of men abandoning the fray.”

So, I put the question to Flake: Even if defeat was likely, why not champion your principles on the campaign trail and let the voters have a choice? He admitted the prospect was tempting. “The pugnacious, competitive part of me wants to go down swinging,” he said.

But ultimately, he determined that any good such a martyrdom might yield would be outweighed by the grim realities of waging a doomed-to-fail campaign. “There are still several things I’d like to accomplish in the Senate this year,” he said. “And to spend every waking minute outside of my duties here dialing for dollars, and to be subjected to the kind of vitriol that comes with politics right now—it just wasn’t worth it.”

The first time I met Flake, it was just a few weeks after Trump’s inauguration, and I had been assigned to profile him for The Atlantic. The junior senator from Arizona had gotten a bit of attention in 2016 for being one of the few Never-Trump Republicans in Congress who held out until the bitter end, and I was interested in seeing how he would navigate the brave new world he found himself in. Over the next several months, I followed him as he trundled through Trump’s America, clinging to his optimism and ideals with his teeth.

I stood in the back of a raucous town hall in Mesa, Arizona, where Flake patiently took questions for two-and-a-half hours from liberal constituents who cursed and booed his every answer. “People here have legitimate concerns and are afraid,” he told me backstage. And I sat in his Capitol Hill office with him and his wife—both of them visibly shaken, and sad—the day after a gunman opened fire on the park where he’d been practicing with his colleagues for the upcoming congressional baseball game. (“Us? Here? Why?” he recalled wondering when the shooting began.)