Story highlights "There's been a long history of Soviet interference going back to the Soviet era in our elections," Clapper said

He said it was unclear if "this interference actually affected the outcome of the election"

(CNN) Former Director of National Intelligence James Clapper said there has never been a case of election interference more aggressive than that involving Russia and the 2016 presidential election.

"There's been a long history of Soviet interference going back to the Soviet era in our elections, but never, ever has there been a case of the aggressiveness and direct actions that the Russians took and their conduct of a multifaceted campaign to interfere with our election," he told CNN's Chris Cuomo Tuesday on "New Day."

Clapper previously testified before a Senate judiciary subcommittee that he was not aware of any evidence demonstrating collusion between President Donald Trump's campaign and Russia -- but he also said he had been unaware of an FBI investigation into the matter until former FBI Director James Comey announced it publicly at a House hearing in March.

"Are you 100% sure that Russia was behind the election meddling that you described," Cuomo asked Clapper Tuesday.

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"Absolutely," Clapper responded. "The evidence, which unfortunately we could not detail in our intelligence community assessment, was, in my view, overwhelming. And that is why the assessment that we did enjoyed such a high confidence level."

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