Here is more from The New York Times:
Invited to think tanks to discuss arms control, he would invariably offer an unapologetic defense of Russia’s intervention in Ukraine and assail Americans for what he portrayed as their hypocrisy — then afterward approach a debating partner to suggest dinner.
“Not all of us, myself included, initially appreciated his very tough, in-your-face style,” said Dimitri K. Simes, president of the Center for the National Interest and an advocate of closer Russian-American relations, who hosted a dinner at his home for Mr. Kislyak after his arrival in Washington and regularly invited him to events at his center. “But we gradually came to develop a grudging respect for him as someone who was really representing the positions of his country.”
Mr. Simes introduced Mr. Kislyak to Mr. Trump in a receiving line last April at a foreign policy speech hosted by his center at the Mayflower Hotel in Washington. Mr. Kislyak was one of four ambassadors who sat in the front row for Mr. Trump’s speech at the invitation of the center. Mr. Simes noted that Mr. Sessions, then a senator from Alabama, was there, but he did not notice whether he and the ambassador spoke at that time.
Here is a Democratic National Committee (DNC) email obtained by WikiLeaks which paints Simes as pro-Russian.
Think tank expert Matthew Rojansky of the Wilson Center, who speaks regularly with Kislyak, says he thinks it is unlikely that Kislyak is a spy.
Kislyak has spoken at the Center for Strategic and International Studies (CSIS) on several occasions, as well as at other think tanks like the Carnegie Endowment for International Peace.