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First, let’s try a little thought experiment: Whenever President Trump starts talking about NATO, imagine what Vladimir Putin would want Trump to say. Then compare it to what Trump actually says. The two are often frighteningly similar.

The pattern continued yesterday and today, with Trump disparaging NATO members on Twitter, on his way out of Washington and again when arriving at the NATO summit in Europe. Why is Trump doing this? I don’t know. But I do know the effect it’s having. Defying his own aides and senators from both parties, the president of the United States is jeopardizing the Western alliance that has done so much good over the past seven decades — and he is comforting Western Europe’s biggest modern enemy, Putin’s Russia.

Related: “Trump Is Training His Base to Hate NATO and Like Putin,” by Jonathan Chait, in New York magazine. In the same publication, Heather Hurlburt writes, “The Trump administration has taken repeated concrete steps to damage European and international institutions and specific European governments.”