The showdown between President Donald Trump and Sen. Jeff Flake turned out to be no contest. It wasn’t Trump who was out of the GOP mainstream, but Flake.

The Arizona senator supported Gang of Eight-style immigration reform, when immigration restriction is becoming a litmus-test issue in the party.

He is a Goldwaterite, libertarian-inflected conservative, when the market for libertarianism within the party is limited and diminishing by the day.

He is frankly anti-Trump, when Trump owns the party. Many Republican voters are fully aware of the president’s flaws, but they don’t want to hear about them constantly from Republican officeholders.

Flake’s criticisms of the president were honest, sincere and principled. If he’s not a finalist for a Profile in Courage Award, the John F. Kennedy Library Foundation is falling down on the job.

They were also malpractice. The most likely outcome was, at the very least, to make it more difficult to defeat the Trumpite insurgent Kelli Ward in a primary next year, which one would have thought was a paramount political goal.

Worse, Flake apparently rendered himself unelectable. Perhaps he considered speaking out more important than serving, a personal choice that no one can gainsay. But if the party isn’t going to be overrun by Trump sycophants, it will need working politicians who are willing and able to better navigate these waters.

There are a few, more sensible approaches in the Senate.

There’s the Ben Sasse model — speak your mind without fear or favor, knowing that you aren’t facing a tough primary in a matter of months and, if you decide to run again, it won’t be until 2020, when the mood might have shifted.

There’s the Mitch McConnell model — hold your cards as close to the vest as possible and try to keep things from running completely off the rails so the party’s congressional majorities aren’t destroyed.

There’s the Lindsey Graham model — criticize Trump when he’s wrong and never abase yourself in his defense, but develop a relationship with the president to maximize your sway.

But it’s a mistake to assume that Trump will somehow magically evaporate, leaving everything in the party as it was before he showed up. At this point, a Trump failure will take down the party, too, and may deepen and intensify the Republican civil war rather than end it.

It’s also a mistake to treat the Trump phenomenon as a fluke from which Republicans need learn no lessons. Establishment Republicans seem to believe Trump’s rise says more about the inadequacies of their voters than about the inadequacies of their own, shopworn politics.

This was the problem with George W. Bush’s speech attacking the president and Trumpism. Bush unquestionably has the standing to criticize Trump’s character and conduct. Substantively, though, the speech had a strong whiff of nostalgia and betrayed no self-awareness of how Bush’s failures, real and perceived, contributed to the rise of Trump.

Bush isn’t even really taking account of the sources of his own support. He denounces nationalism, yet the wars in Afghanistan and Iraq had significant nationalist backing at the outset and, when they lost it over time, became unpopular and unsustainable.

Trumpism won’t reign forever. Whatever comes next in the party is likely to borrow from his populism and nationalism, and certainly won’t snap all the way back to Bushism.

The great advantage Trump has in Republican politics is that he’s a Republican president, and partisanship is an awesome political force. So is the cult of personality that inheres in the presidency, augmented by Trump’s celebrity. He has the right enemies, and his culture-war fights coupled with his traditional GOP legislative agenda offer something for everyone in the party, from the populists to the Chamber of Commerce.

All of this means that, until further notice, he occupies the commanding heights of the GOP. Full-frontal assaults may be bold and brave, but they will likely be ineffectual, if not wholly counterproductive.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.