In the first weeks of the Obama Administration, Michael McFaul, the President’s top aide on Russia policy at the National Security Council, found himself in a contentious negotiation with Sergey Kislyak, the Russian Ambassador to the United States. McFaul, a political scientist at Stanford who focussed on democracy promotion, was in his first government job. Kislyak, who is thirteen years older, was one of Russia’s most experienced diplomats. “He expected that I was going to be this neocon hawk on Russia,” McFaul told me. “And so he had his dukes up. He was ready for a fight.”

Obama had inherited a plan for an aggressive missile-defense system for Eastern Europe that was a major irritant to Moscow. Kislyak, who studied physics, was an expert on arms control, and explained that the system was not solely defensive, as the Bush Administration had insisted. A radar system to be deployed in the Czech Republic was of particular concern to Kislyak.

“I was the new guy, so I was willing to listen,” McFaul, who later became Obama’s Ambassador to Russia, said. “He was lecturing me about the dual capabilities of that radar and that it had capabilities against Russia. And I said, ‘That’s news to me.’ And he said, ‘Well, you need to learn.’ ”

Kislyak, who has been the Russian Ambassador to the United States since 2008, had a point. The radar was not strictly defensive. “He was right about that one,” McFaul said. The Obama Administration later scrapped the plan, including the Czech radar station, a decision that was partly related to Obama’s attempted “reset” with Moscow.

During the Obama years, as the U.S.-Russia relationship deteriorated, Kislyak, who is known for cultivating deep ties in Washington, went into overdrive trying to explain the Russian position. A few years ago, I attended a lunch at the Russian Ambassador’s residence on Sixteenth Street, a short walk from the White House, where Kislyak, a large and unprepossessing man, offered the Russian perspective to a skeptical group of reporters. “People that don’t know him well and see his gruff style, and his toeing the public line when he’s speaking publicly, underestimate how persistent he is at nurturing these kinds of relationships with people throughout the city,” McFaul said.

Part of Kislyak’s success is that he can turn the stereotype of the severe Russian diplomat on its head. An Ambassador from Europe noted that, during a public debate he had with Kislyak, over Russia’s annexation of Crimea, Kislyak exceeded expectations. “I thought I had the much better case, but he acquitted himself so well because he was so smooth and friendly and soft-spoken,” the Ambassador said. “He could have been rough and abrasive and a Putin-style Russian Cold Warrior, which he was not. He played it very softly. Because he was not what people expected him to be, he ingratiated himself with the audience. ”

Kislyak attends Donald Trump’s address to a joint session of Congress, on Tuesday. PHOTOGRAPH BY BRENDAN SMIALOWSKI / AFP / GETTY PHOTOGRAPH BY BRENDAN SMIALOWSKI / AFP / GETTY

This approach occasionally paid off. There was the early deal over missile defense. One of the bright spots in U.S.-Russia coöperation came in 2015, when both countries championed the Iran nuclear agreement. Kislyak and his colleagues from European countries toured congressional offices to make the case for the deal. “He didn’t play the Russian card,” the European Ambassador said. “He was a team player.”

“I’ve known him since I was in the Clinton Administration,” Strobe Talbott, Clinton’s Deputy Secretary of State and now the head of the Brookings Institution, said. Talbott noted that Kislyak was especially adept at negotiating nuclear agreements after the Cold War ended. “He is very expert on the technology of arms control, which was still big then. He’s very good on the geopolitical stuff and the domestic political stuff. Not shy, very understated.”

Despite the high regard in which he was held, Kislyak increasingly found that he had almost no audience in Washington. During a November talk at Stanford hosted by McFaul, Kislyak said that it was “the worst point of our relations after the end of the Cold War.” There was almost no contact between the two sides during the last two years of the Obama Administration. “We have learned during these two years to live without you, and you have learned to live without us,” Kislyak said.

During that lull, Kislyak’s attention seemed to drift to a new target: Donald Trump and his advisers. In July, at the Republican National Convention, and in September, Kislyak met with Jeff Sessions, who at the time was Donald Trump’s most high-profile supporter in the Senate, the Washington Post reported on Wednesday. Sessions concealed the meetings from a Senate committee during his confirmation hearing as Trump’s nominee for Attorney General. This week, after the meetings were reported, Sessions insisted that he met with Kislyak only in his capacity as a member of the Armed Services Committee. McFaul scoffed at that idea. “He’s meeting with Senator Sessions because of his relationship to Trump, not because of what he does on the Senate Armed Services Committee,” he said. “We now know he’s the Attorney General, but back then he was talked about for all kinds of jobs, including Secretary of Defense.”

Michael Flynn, Trump’s former national-security adviser, had several conversations with Kislyak during the transition. In December, he met with Kislyak at Trump Tower, along with Jared Kushner, to “establish a more open line of communication in the future,” according to the White House. Later that month, after the Obama Administration kicked out Russian diplomats and instituted economic sanctions, Kislyak and Flynn had phone conversations in which they discussed the future of those sanctions. Flynn’s effort to conceal those talks led to his resignation, last month.

For Kislyak, the Trump team would have been a welcome change. Carter Page, an oil-industry consultant who briefly worked on the campaign, was an advocate for rapprochement with Putin. (He is reportedly being investigated by the F.B.I. for his links to Russia.) Paul Manafort, who is also reportedly under investigation, worked for a pro-Russia party in Ukraine before briefly serving as Trump’s campaign manager. Flynn infamously sat next to Putin at a Moscow dinner in 2015 celebrating RT, the Russian television network that broadcasts English-language propaganda. To some extent, they all share Kislyak’s view that America, through NATO and its eastern expansion, has been needlessly hostile to Russia, that Ukrainian democracy and sovereignty is a nuisance issue, and that the U.S. and Russia could be united by the common threat from ISIS.

“We do have a commonality of challenges in the world and, whether you want it or not, it’s the same to you and the same to us,” Kislyak said at Stanford, citing terrorism, religious intolerance, regional conflicts, and climate change. “If I draw a list of things that unite us and one that pull us apart, I would say the first list is much longer. And, in my view, is significantly more important, both to my country and to yours.”

There is nothing inherently wrong with the fact that Flynn, Sessions, and other Trump advisers talked to the Russian Ambassador. With the Kislyak affair, in which multiple conversations between Trump officials and the Ambassador have been concealed, so far, we have a coverup without a crime.