Just when it seems that Donald Trump could not display more ignorance and bad judgment or less of a moral compass, he comes up with another ignominy or two. This weekend he denigrated the parents of a fallen American military hero and suggested that if elected he might recognize Russia’s claims to Ukraine and end sanctions.

Mr. Trump’s divisive views helped him capture the Republican presidential nomination. And even as he creates a political whirlwind with each utterance, leading members of his own party haven’t the spine to rescind their support. Sure, some have come out with strong criticisms, but none have gone far enough. Repudiation of his candidacy is the only principled response.

On Sunday on ABC, Mr. Trump’s comments on Ukraine demonstrated even less knowledge about world affairs than suspected. His remarks also reinforced suspicions that he is sympathetic toward Vladimir Putin, Russia’s authoritarian, anti-Western president.

Mr. Trump seemed confused about Russia’s 2014 annexation of Crimea and its efforts to wrest other parts of the country from Ukraine’s control. “He’s not going into Ukraine, O.K., just so you understand,” Mr. Trump said, apparently unaware that Mr. Putin sent troops there two years ago and that the international community still considers Crimea to be part of Ukraine. Russian troops have been seen, and sometimes killed, in Russian-speaking parts of Ukraine where an insurgency is fighting the Ukrainian government.

The United States and the European Union have condemned the land grab, which is at odds with post-Cold War commitments, and imposed sanctions that Mr. Putin is desperate to have lifted. Mr. Trump’s willingness to support Mr. Putin’s claim on Crimea and other parts of Ukraine, coupled with his lack of commitment to NATO, is good reason for Europe to fear for the future of the alliance if he becomes president.