Representative Devin Nunes, the embattled California Republican who is chairman of the Intelligence Committee, announced on Thursday he would step aside from leading his committee’s investigation into Russia’s efforts to disrupt last year’s presidential election. Mr. Nunes, the Intelligence Committee chairman, said his decision came after “left-wing activist groups” filed accusations against him with the Office of Congressional Ethics.

The Republican chairman of the House Intelligence Committee rebuffed  calls on Tuesday to recuse himself from the panel’s investigation into  Russian meddling in the presidential election, as Democrats accused him of stalling the inquiry by canceling the committee’s meetings.