On Friday, President Donald Trump said the United States had no proof yet that the most prominent Russian opposition leader had been poisoned by the Kremlin.

Not true.

German military scientists had confirmed earlier in the week “100%” that Alexei Navalny was poisoned by one of the world’s deadliest — and internationally banned — chemical agents, developed by the Soviet Union. (Having fallen ill while he campaigned in Siberia, Navalny had been medevaced to a Berlin hospital.)

German Chancellor Angela Merkel called the Navalny case an “attempted murder with a nerve agent” and demanded that Russia explain it. The Kremlin, of course, denied any involvement.

Yet Trump insisted, despite irrefutable evidence, that “we have no proof yet.” He effectively mouthed the Kremlin line while refusing to join other Western leaders in demanding answers from Vladimir Putin.

“No one has any doubts about German science,” says former U.S. ambassador to Moscow Alexander Vershbow. “Trump is just in a never-say-bad-word mode about Putin. This emboldens Putin to do more of the same.”

Whether or not Putin gave the direct order for the Navalny poisoning, political murders have become commonplace on his watch, in Russia and elsewhere in Europe. At a time when democratic norms are under severe threat worldwide, Putin’s murderous modus operandi further undermines them.

The list of unsolved political murders of Putin critics is so lengthy the world has almost grown to accept them as normal Russian behavior. The attack on Navalny with a banned chemical weapon should shake that complacency.

Poison may have been a favored tool of Russian tsars and Soviet agents, but Putin promotes himself as a pre-eminent global leader for the current era. Trump wants to invite him to the White House.

The Navalny affair reminds us it is long past time to stop accepting Putin as a normal leader.

A very partial list of unsolved murders of Putin’s opponents reflects the abnormality of Russia’s president, and why Trump’s refusal to criticize him is abnormal as well.

The dead include the American editor of Forbes Russia, Paul Klebnikov in 2004, and the brave Russian journalist Anna Politkovskaya, who survived a poison attack only to be gunned down in 2006.

Yuri Shchekochikhin, an investigative journalist specializing in corruption, died mysteriously days before planning to meet FBI investigators in the U.S. His colleagues are convinced he was poisoned.

Leading opposition figure Boris Nemtsov was shot dead in 2015 right under the Kremlin’s walls as he strolled on a bridge with a friend. This perfectly illustrates Putin’s sense of impunity.

And the poison attacks on Putin’s opponents grow ever more daring. In 2004, Ukraine’s former pro-Western President Viktor Yushchenko was poisoned with dioxin, he believed by Russian agents. At the Davos World Economic Forum in 2005, Yushchenko told me he believed he could trace the trail of the killer to Moscow.

In 2006, Russian defector Alexander Litvinenko, who had British citizenship, was poisoned in London by radioactive polonium-210, inserted into a cup of tea by Russian agents. A British public inquiry into Litvinenko’s death concluded that Putin probably approved his assassination. Of course, the Kremlin denied all and promoted the alleged killer to membership in parliament.

And in 2018, Sergei Skripal, a double agent for the U.K.’s intelligence services, and his daughter, Yulia, were poisoned in Salisbury, England, also with a Novichok nerve agent. The British government accused two Russian agents of the murder attempt, but the Russian foreign ministry called the allegations “insane.”

This is the Russian government whose leader Trump has been defending for the past four years. In December 2015, when asked about political murders on Putin’s watch, Trump told ABC: “Nobody has proven that he’s killed anyone. ... He’s always denied it.” When asked the same question on MSNBC’s Morning Joe, candidate Trump answered, “Well, we do a lot of killings, too.”

Trump’s indifference to Putin’s mainstreaming of assassinations hasn’t changed since 2015. Indeed, the president has demanded that the Russian leader be reinvited to G-7 meetings of the major industrialized democracies.

Meantime, Trump refuses to confront Putin on Russian bounties for the killing of U.S. soldiers in Afghanistan, or Russian threats to U.S. troops in Syria.

Nor will the president stand up to Russia’s efforts to target our 2020 election with disinformation, including false claims that mail-in voting could lead to fraud, efforts the U.S. intelligence community has publicly warned about. Perhaps this is because Trump is making the same false claims that Moscow is amplifying.

When the Kremlin used Novichok on British soil in 2018, Trump did agree to sanctions, pressed by London.

Now Merkel is demanding a collective NATO response to the Navalny poisoning, and may even put the future of an almost completed $11 billion Russian gas pipeline on the line.

Yet Trump still refuses to criticize a Russian leader who normalizes the murder of political opponents. Perhaps the U.S. president envies the ease with which Putin can eliminate them.

Whatever Trump’s reasons, the Navalny case is testing him as well as Putin. Two months before the election, Trump’s continued refusal to take a strong stand on the poisoning of Navalny is a blatant sign of his indifference to democratic norms.