I encountered and am aware of information and intelligence that revealed contacts and interactions between Russian officials and U.S. persons involved in the Trump campaign," Brennan testified. "I know what the Russians try to do. They try to suborn individuals and they try to get individuals, including U.S. persons, to act on their behalf, either wittingly or unwittingly. And I was worried by a number of the contacts that the Russians had with U.S. persons and so therefore, by the time I left office on Jan. 20, I had unresolved questions in my mind as to whether or not the Russians had been successful in getting U.S. persons, involved in the campaign or not, to work on their behalf, again, either in a witting or unwitting fashion. And so therefore I felt as though the FBI investigation was certainly well-founded and needed to look into those issues