Read: Three remarkable things about Michael Cohen’s plea

As a candidate, Trump said in a tweet that he had “ZERO investments in Russia.” Shortly before his inauguration, he tweeted that he had “NOTHING TO DO WITH RUSSIA—NO DEALS, NO LOANS, NO NOTHING!” Yet he has a long history of Russian customers and financial backing, as the Washington Post foreign-affairs columnist David Ignatius explained last year. Before his inauguration, Trump also said that he had “no deals that could happen in Russia, because we’ve stayed away.” But last week, Cohen said he had been working on a Trump Tower deal in Moscow up until June 2016 (CNN lays out the timeline here) and lied about it to Congress to preserve the “political messaging” about the Trump Organization’s dealings in Russia.

Democrats say Trump’s misleading statements about his business connections to Russia gave Putin’s regime compromising material, or kompromat.

“They knew that he had major business dealings, or that Cohen, on his behalf, had major business dealings in Moscow during the campaign, and that he was lying about that. There may be other things that they know that give them leverage,” Representative Jerry Nadler, the New York Democrat soon to take over the House Judiciary Committee, said Sunday on NBC’s Meet the Press. He argued that “the fact that he was lying to the American people about doing business in Russia and that the Kremlin knew he was lying gave the Kremlin a hold over him. And one question we have now is, Does the Kremlin still have hold over him, because of other lies that they know about?”

Read: The Democrat who could lead Trump’s impeachment isn’t sure it’s warranted.

“One question has always been, Why was the president so obsequious to Putin from the beginning of the campaign up to the present day?” Nadler said. “And it may be that it’s because the Kremlin has leverage over the president, which is a terrible thing if true.”

Senator Mark Warner of Virginia, the top Democrat on the Senate Intelligence Committee, was more reserved but still critical. “I have got to believe that most Republicans who were about to nominate Donald Trump in the summer of ’16 would probably have thought it was a relevant fact—they would like to have known that then-candidate Trump was still trying to do business with Russia,” Warner said on CNN’s State of the Union. He added that he’s withholding a final judgment about possible collusion until the committee’s investigation finishes, to ensure that bipartisan work continues with Republican Senator Richard Burr of North Carolina, the committee chairman.

However, Warner asked pointed questions that expressed the developing theory to explain the president’s deference to Russia and its leader: “Why was Donald Trump, who was willing to whack almost anyone, never willing to say an ill word about Vladimir Putin? … Was it because of his potential business dealings with Russia?” Or, he asked, was it because there was communication with the Russians, possibly through Roger Stone, a longtime Trump adviser, about their hacking of Democratic emails and their plan to release them through WikiLeaks?