Republican presidential nominee Donald Trump speaks during a news conference in Doral, Fla., on July 27. (Evan Vucci/Associated Press)

THE FBI is investigating the theft of some 20,000 emails from servers of the Democratic National Committee, even as U.S. intelligence agencies are reported to have told the White House they believe Russia is responsible. The hack and the release of the emails to the WikiLeaks website are offenses that, if traced to the regime of Vladi­mir Putin, would justify sanctions or other retaliation. Republican vice-presidential candidate Mike Pence understands that: On Wednesday, he said that if Russia is “interfering in our elections, I can assure you both parties and the United States government will ensure there are serious consequences.”

Donald Trump, on the other hand, is inviting more such interference. “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” he said at a news conference, referring to messages that were deleted from Hillary Clinton’s private server. No, he wasn’t joking, as apologist Newt Gingrich suggested; Mr. Trump later repeated the suggestion in a tweet.

Let’s be clear about what this means: The Republican candidate for president has invited a hostile foreign power to conduct an unlawful cyberattack against his opponent and to make public emails she deemed personal and private. Washington has been wondering whether Mr. Putin is attempting to tip the U.S. election to Mr. Trump. Now Mr. Trump is openly appealing to him to do so.

Mr. Trump said he has “ nothing to do with Putin” and has never spoken with him, though in the past he has bragged about having done so. He denied that he has business interests in Russia, which doesn’t explain why his son would have said Russian money plays a “disproportionate” role in “a lot of our assets.” He again said he would not release his tax returns, which means his claims cannot be verified.

Mr. Trump did provide more evidence of why Mr. Putin might be eager to support him. After repeating his disparagements of the NATO alliance, he was asked if his administration would lift sanctions on Russia and recognize its annexation of Crimea, the Ukrainian territory that it invaded and occupied in 2014. “We’ll be looking at that. Yeah, we’ll be looking,” Mr. Trump responded, suggesting a stark reversal of the stance taken by the United States and its European allies. You could almost hear the champagne corks popping in the Kremlin.

Retired Navy admiral and law professor John Hutson used his speech at the Democratic convention to question Donald Trump's ability to keep America safe. (The Washington Post)

Once again, Mr. Trump’s position is diametrically opposed to that of his own party’s leaders. A spokesman for House Speaker Paul D. Ryan (Wis.) said “Russia is a global menace led by a devious thug,” and Mr. Putin “should stay out of this election.” We’ve already cited Mr. Pence, who was only restating what, until now, has been the common position of U.S. political leaders from left to right: Cyberattacks by foreign governments such as Russia and China against U.S. industry, government and other sensitive targets are unacceptable and must be resisted. There should, indeed, be “serious consequences” for Russia if it is found responsible for the DNC hack. And voters should take note of one more reason Mr. Trump must not acquire the powers of the presidency.