All these charges have deafening echoes today. But this time, the credulous appeaser failing our allies is a Republican president. For communist dictators such as Xi Jinping and Kim Jong Un, Trump exudes admiration and amity. To the anti-Western Russian President Vladimir Putin, he offered congratulations for winning a rigged election.

When it comes to Canada’s Justin Trudeau and Germany’s Angela Merkel, by contrast, he seethes with resentment. With Trump, it’s better to be a long-standing American adversary than a faithful ally.

That about-face strains belief. More incredible still is that the Republican Party has chosen to follow his lead. GOP leaders and conservative commentators have turned themselves inside out praising behavior they would have torched had it come from a Democratic administration.

This new outlook might be defensible if it were the product of a conscious, informed reassessment of our role in a changing world. But it’s not. It’s almost entirely the product of the takeover of the Republican Party by Trump. Anything he says immediately becomes its semiofficial policy—no matter how deeply it contradicts past doctrines.