WHEN IT comes to American democracy, the attack on the presidential election in 2016 is no joking matter — and no mystery. Russia’s military intelligence service stole campaign emails and leaked them to help candidate Donald Trump, while streams of incendiary social media posts and online ads were paraded before American voters. After all that, Mr. Trump on Friday kissed off the concerns, once again.

At the outset of his meeting with Russian President Vladimir Putin at the Group of 20 meeting in Osaka, Japan, Mr. Trump was asked about the election meddling. He lifted a finger, pointed it at Mr. Putin and joked, “Don’t meddle in the election.” He was dismissive and halfhearted when the moment called for a serious and firm statement. Mr. Putin surely grasped the import of Mr. Trump’s lame gesture. He got away with it and can again.

To make matters worse, Mr. Trump then launched into another screed against the media in front of Mr. Putin. “Get rid of them,” Mr. Trump said, referring to the pool reporters covering the meeting. “ ‘Fake news’ is a great term, isn’t it? You don’t have this problem in Russia, but we do.” Mr. Putin, in a rare public remark in English, replied, “We also have. It’s the same.” Mr. Trump’s remark was an unctuous display of his personal strongman impulses in front of a Russian president who leads a system that imprisons, persecutes and kills journalists and dissidents who become too curious or critical.

This is no time to joke. Today’s generation of autocrats and tyrants cynically uses the trappings of democracy while subverting freedom from within. The U.S. president should stand as a guardian against this threat, but instead Mr. Trump inexplicably cedes the field to Mr. Putin. During an interview with the Financial Times published on Friday, Mr. Putin airily brushed off a question about the “alleged interference” in the 2016 election. “What happened in reality?” he asked. “Mr. Trump looked into his opponents’ attitude to him and saw changes in American society.” Thus, Mr. Putin happily skates away from any responsibility with a bit of Kremlin trickery: lie, deny and divert attention.

Perhaps to be taken more seriously is Mr. Putin’s confident declaration in the Financial Times interview that “the liberal idea has become obsolete.” The way to read this remark is that Mr. Putin, along with other foes of democracy, including President Xi Jinping of China, wants to declare victory for illiberal authoritarianism, with which he can enrich himself and his cronies while extinguishing his enemies. He and, even more, Mr. Xi are harnessing to their authoritarian ends technologies that were once thought bound to extend freedom.

But the battle Mr. Putin declares won is not over. The desire to live in liberty burns strongly in their lands, as in ours. What the United States needs at this critical juncture is to lead the world in showing why a free people, a free press, and the freedom to speak, worship, assemble and travel are not and never will be obsolete. Mr. Trump is not capable of playing that role, but hopefully a new president will be.

Read more: