He’s said before that he thinks a conservative probably *will* challenge Trump in 2020 but this may be the first time he’s said a conservative *should* challenge him. And it’s not hard to guess who that challenger is likely to be. The universe of conservatives willing to primary POTUS is small, partly because the, ah, universe of conservatives is small. Within that universe, even hardcore anti-Trumpers like Ben Sasse will decline to jump in knowing that doing so would cost them their jobs. Even Mitt Romney, possibly the right’s most prominent Trump critic, is off the board now that he’s decided to focus on the Senate.

Off the top of my head, the number of conservatives with governing experience, a bit of national name recognition, contempt for Trump, and little to lose by mounting a doomed primary challenge includes Flake, Bob Corker, maaaaaybe Tom Coburn, and that’s it. And of those three, Flake clearly seems most enamored with the idea of a “battle for the soul of the Republican Party.”

So yeah, it’s probably going to be him.

Why would Flake fight a battle for the soul of the party knowing he’s sure to lose? I tried piecing through that a few months ago and still can’t settle on a convincing theory. He won’t win, won’t get close to winning, will be torched hour by hour by Trump’s fans, will be torched by liberals demanding to know why he voted with Trump 95 percent of the time or whatever, will alienate party honchos who might otherwise consider him for jobs after leaving the Senate, and likely won’t get nearly as much media coverage as he expects a Trump primary challenger will receive. He’s a low-key guy, after all; his criticism of Trump is harsh on the merits but it’s always delivered with a smile, almost sotto voce. That’s not what the media wants from a right-wing Trump opponent. They want blood and entertainment. A livelier interview subject like Sasse would get more airtime, as he might land enough roundhouses to bait Trump into responding to him. As it is, POTUS is likely to ignore Flake entirely on the trail. After the first burst of breathless “Republican Flake challenges Trump!” coverage, he’s apt to become an afterthought. Within a few months his campaign will largely be a rumor, kept barely alive by fans at National Review and the Weekly Standard.

If he runs I think he’ll do it as a matter of what he regards as civic duty, believing that the president’s vision for the country generally and for the right specifically is all wrong and someone must present an alternative, doomed or not. Since he’s the most high-profile person in America willing to present that alternative, the duty falls to him. Plus, as a matter of self-interest, it’s not a bad legacy play. The odds of a conservative resurgence within the next few decades look mighty small to me, but if it happens then Flake’s quixotic primary challenge could end up romanticized in hindsight by the new generation as a lonely quest to restore honor and small-government principle to the GOP. He might become a celebrated figure, even a prophetic one if Trump wins reelection and his second term brings disaster.

But even that seems overly optimistic for Flake. You can imagine the GOP shifting gradually from populism back to conservatism but it’s harder to imagine them shifting from tribalism to a politics of principle. However much luster may return to small government as a model, Flake will still be guilty of having sinned grievously against the tribe by opposing a sitting Republican president in 2020. If Trump ends up losing the election, Flake will be scapegoated as having caused it by weakening him with his criticisms during the primary. Every sin of the ensuing Democratic administration will be laid at his feet. Right, right — things worked out okay for Reagan in 1980 after he tried to blow up Gerald Ford in 1976 and Ford ended up losing the presidency, but Reagan was the populist warrior trying to unseat the establishmentarian. A Flake/Trump primary would be the opposite, an establishment Republican attempting to unseat the people’s choice. He won’t soon be forgiven by his party, I expect.