In some sense, many analysts have said, he is right: Efforts by a hostile foreign power to influence an American presidential election — with or without the assistance or knowledge of the winning candidate — may well be a scandal “bigger than Watergate!”

The F.B.I. and a team of special prosecutors are investigating whether any of Mr. Trump’s associates were coordinating with Russia to help Mr. Trump defeat his Democratic rival, Hillary Clinton. And, since the appointment of the special counsel, Robert S. Mueller III, the investigation has expanded to include inquiries into whether Mr. Trump has attempted to obstruct justice to bring an end to what he regularly calls a witch hunt.