He’s not ruling anything in or out in terms of running himself, but c’mon. Flake is almost uniquely ill-suited to challenge Trump whether in the primary or as an indie in the general. He’s a libertarian, a rump part of the conservative rump within the GOP. Ask Rand Paul how well libertarians do in Republican primaries, especially when they’re not the most anti-establishment candidate onstage, as his dad was in 2012. Flake’s constituency within the party is now so small that he retired rather than face a weak, fringe-y primary challenger in Kelli Ward knowing that all indications are that she would have beat him.
If he primaried Trump he’d pull 15-20 percent of the Republican vote, purely as an anti-Trump protest. He’d spent most of his time criticizing Trump for being authoritarian and reactionary and a bit of his time calling for smaller government and open borders on trade and immigration, but he’s too soft-spoken to use the primary spotlight to do much rhetorical damage to POTUS. At every turn he’d be peppered with questions as to why he voted with the president so many times in the Senate if he finds his agenda so objectionable. Meanwhile, if instead he ran as an independent, he might not do any better than Gary Johnson did last year. For an obvious reason: He’s not a centrist! He has a reputation for being one because he’s pro-amnesty and spends a lot of time talking about the importance of civic institutions (mere cuckery!) but Democrats would recoil from his libertarianism. If his goal is simply to try to tank Trump’s chances by pulling votes from the right, enabling a Democratic victory, *maybe* he could achieve that in a very tight race. But he wouldn’t threaten the Democratic nominee at all.
In fact, the irony of Flake wringing his hands over Trump’s alleged extremism is that it’s the left’s drift towards the opposite ideological pole that makes the odds so long for a successful independent candidacy. His theory here seems to be that if Democrats nominate a socialist like Bernie Sanders or Elizabeth Warren, there’ll be a significant minority of centrist Democrats who’ll turn up their noses and look around for a third-party candidate. There’s no reason to believe that’s true. Trump was a bigger break with his party’s orthodoxy, both ideologically and temperamentally, than either Sanders or Warren would be for Democrats and yet Republicans supported him almost uniformly in the name of defeating his odious opponent. Centrist Dems would do the same for their nominee against Trump, a president who sometimes polls in the low single digits among their party in job-approval measures.
Besides, the universe of people who could plausibly run as a centrist independent and attract meaningful support is small and shrinking by the day. Mike Bloomberg is the name perennially mentioned but Bloomberg would be 78 on Election Day 2020. (Of course, Bernie Sanders would be 79.) If he was going to run he would have done it by now. John Kasich *is* probably going to run — why else would he be publishing op-eds on North Korea in WaPo? — but Democratic voters aren’t going to cross the aisle to vote for a Republican with no chance of getting to 270 knowing that dividing their vote means increasing the odds that Trump will win a three-way race. Kasich is a charmless guy, too; at a minimum a successful independent candidate should have charisma to burn.
If Flake, Bloomberg, and Kasich really want to stop Trump, they should do what little they can to boost a bland Democrat in the 2020 primaries who can run as a pure Not Trump candidate. It worked like a charm for Doug Jones in Alabama, it’ll probably work nationally if POTUS’s job approval remains stuck around 40 percent. But the left isn’t going to accept some centrist-ish unknown quantity next time after having been made to suck it up for Hillary in 2016. Republican populists got their pick as nominee, now progressives want their turn.