Rep. Jerry Nadler said Sunday that the revelations from President Trump’s former personal attorney are proof that Russia had “leverage” over Trump during the 2016 presidential campaign.

Speaking on NBC’s “Meet The Press,” Nadler, D-N.Y. – who is poised to become the next chairman of the House Judiciary Committee – said that Michael Cohen’s admission last week about his role in securing a Trump Tower in Moscow during the time of the GOP presidential primary shows that Trump was a compromised candidate, and now president, and that that should be worrying to the American public.

"There certainly was leverage during the campagin period and until recently, because they knew that he was lying that he had major business dealings with Cohen on his behalf during the campaign and that he was lying about that -- there may be other things that they know that give them leverage," Nadler said.

He added: "The fact that he was lying to the American people about doing business in Russia and the Kremlin knew he was lying gave the Kremlin a hold over him," Nadler said. "One question we have now is: Does the Kremlin still have a hold over him because of other lies that they know about?"

Nadler’s comments come days after Cohen pleaded guilty to lying to Congress about negotiations he says he had on Trump's behalf for a real estate deal in Moscow.

Though he told lawmakers the talks were done by January 2016, he admitted they actually lasted as late as June — after Trump had secured the Republican nomination and after Russians had penetrated Democratic email accounts for communications later released through WikiLeaks. Cohen also said he had briefed Trump and members of his family about the project's progress.

Cohen said he lied out of loyalty to Trump, who insisted throughout the campaign that he had no business dealings in Russia, and to be consistent with his political messaging.

Though the Cohen plea didn't directly connect to Trump's campaign, other cases have.

George Papadopoulos, a former Trump campaign adviser, pleaded guilty to lying to the FBI about April 2016 conversations with a Maltese professor who told him Russians had "dirt" on Hillary Clinton in the form of "thousands of emails." Papadopoulos told the FBI he wasn't part of the campaign when he encountered the professor, Joseph Mifsud, even though he had joined weeks earlier.

His lawyers said Papadopoulos, now serving a 14-day prison sentence, "lied to save his professional aspirations and preserve a perhaps misguided loyalty to his master."

Trump's former national security adviser, Michael Flynn, is being sentenced later this month after admitting lying to the FBI by saying he didn't discuss sanctions against Russia during the transition with Sergey Kislyak, the Russian ambassador to the U.S. at the time.

That deception was flagged for the White House in January 2017 by Obama administration holdover Sally Yates, who as acting attorney general told White House counsel Don McGahn that officials were misleading the public by falsely declaring Flynn hadn't discussed sanctions.

Flynn's guilty plea was especially significant in that it made clear other transition officials were aware of his Kislyak conversations and discussed with him what he would say. And while Flynn was fired in February 2017, his importance to Trump became evident when ex-FBI Director James Comey said Trump had encouraged him during a private meeting that same month to end an investigation into Flynn.

This week, prosecutors accused former Trump campaign chairman Paul Manafort of lying even after his guilty plea, though they have not released specifics regarding the alleged lies.

"We have a president who lies incessantly to the American people about big matters and small matters, who surrounds himself with people who lie incessantly to the American people,” Nadler said. “The key fact now is that the time that he can get away with lying to the American people all the time and evading accountability is coming to an end.”

Sen. John Barrasso, R- Wyo., who also appeared on “Meet The Press,” downplayed Cohen’s guilty plea and his revelations about Trump’s role in the process.

"The president is an international businessman. I’m not surprised he was doing international business,” Barrasso said. “Cohen is in trouble for lying to Congress, not anything related to the campaign or Russian influence.”

Barrasso defended the president against fears from Democrats that Special Counsel Robert Mueller would be fired and slammed Democrats for their calls that the government shouldn’t be funded without an assurance that the Mueller investigation will be able to continue.

"They’ve been crying wolf for two years that Mueller was going to be fired,” he said. “Didn’t happen, not going to happen.”

The Associated Press contributed to this report.