The latest revelations about Russia and President Trump’s campaign are useful because they might help unravel the mystery that has always been at the center of this story. Why has Trump had such a rosy attitude toward Russia and President Vladimir Putin? It is such an unusual position for Trump that it begs for some kind of explanation.

Unlike on domestic policy, where he has wandered all over the political map, on foreign policy, Trump has held clear and consistent views for three decades. In 1987, in his first major statement on public policy, he took out an ad in several newspapers that began, “For decades, Japan and other nations have been taking advantage of the United States.” In the ad, he also excoriated “Saudi Arabia, a country whose very existence is in the hands of the United States,” and other “allies who won’t help.”

This is Trump’s worldview, and he has never wavered from it. He has added countries to the roster of rogues, most recently China and Mexico. On the former, he wrote in his presidential campaign book, “There are people who wish I wouldn’t refer to China as our enemy. But that’s exactly what they are.” During the campaign, he said: “We can’t continue to allow China to rape our country.” A few months before announcing his candidacy, he tweeted, “I want nothing to do with Mexico other than to build an impenetrable WALL and stop them from ripping off U.S.”

Trump is what historian Walter Russell Mead calls a “Jacksonian” on foreign policy (after Andrew Jackson), someone deeply skeptical and instinctively hostile toward other nations and their leaders, who believes in a fortress America that minds its own business and, if disturbed, would “bomb the s---” out of its adversaries and then retreat back to its homeland.

This was Trump’s basic attitude toward the world, except for Russia and Putin. Ten years ago, when Russian money was pouring into the West, Trump began praising the country and its leader: “Look at Putin . . . he’s doing a great job in rebuilding the image of Russia and also rebuilding Russia period.” In 2013, Putin wrote an op-ed in the New York Times to try to dissuade the Obama administration from responding to the Syrian government’s use of chemical weapons. In it, he argued that the poison gas was actually used by the Syrian opposition to trick Washington into attacking the regime. Trump’s reaction was lyrical. “I thought it was an amazingly well-written . . . letter. . . . I think he wants to become the world’s leader, and right now he’s doing that.”

Trump so admired Putin that he imagined that the two of them had met, making some variation of that false claim at least five times in public, and playing down any criticisms of him. “In all fairness to Putin, you’re saying he killed people. I haven’t seen that,” he said in 2015. “Have you been able to prove that?” When confronted on this again earlier this year, he dismissed it, saying, “We’ve got a lot of killers. What, you think our country’s so innocent?” Trump could not have been making these excuses for any political advantage. The Republican Party was instinctively hostile toward Russia, though in a sign of shifting U.S. alignments, Republicans today have a more favorable view of Putin than Democrats by 20 points.

“There’s nothing I can think of that I’d rather do than have Russia friendly,” Trump declared at a news conference last July. His campaign seemed to follow this idea. He appointed as a top foreign policy adviser Michael Flynn, a man who had pronounced pro-Russian leanings and, we now know, had been paid by the Russian government. Paul Manafort, who was for a while the head of Trump’s campaign, received millions of dollars from Ukraine’s pro-Russia party. During the Republican convention, there was a very unusual watering down of hawkish language on Russia’s invasion of Ukraine. And once elected, Trump chose as his secretary of state Rex Tillerson, who had been awarded one of Russia’s highest honors for foreigners and had a “very close relationship” with Putin. Finally, there are the repeated contacts between members of Trump’s campaign and family with key Russian officials and nationals, which again appear to be unique to Russia.

It is possible that there are benign explanations for all of this. Perhaps Trump just admires Putin as a leader. Perhaps he has bought in to the worldview of his senior adviser Stephen K. Bannon, in which Russia is not an ideological foe but a cultural friend, a white Christian country battling swarthy Muslims. But perhaps there is some other explanation for this decade-long fawning over Russia and its leader. This is the puzzle now at the heart of the Trump presidency that special counsel Robert S. Mueller III will undoubtedly try to solve.

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