The president has been adamant that the meddling did not alter the outcome of the race, but it has become a political cudgel for his opponents.
Many Democrats and some Republicans have raised alarms that the president may have tried to obstruct justice by firing Mr. Comey. The Justice Department’s newly appointed special counsel, Robert S. Mueller III, was given the authority to investigate not only potential collusion, but also related allegations, which would include obstruction of justice.
The F.B.I.’s investigation has bedeviled the Trump administration, and the president personally. Mr. Comey publicly confirmed the existence of the investigation in March, telling Congress that his agents were investigating Russian efforts to influence the outcome of the presidential election and whether anyone in the Trump campaign had been involved. Mr. Trump has denied any collusion and called the case a waste of money and time.
At first, the White House said Mr. Trump fired Mr. Comey based on the recommendation of the Justice Department, and because of Mr. Comey’s handling of the F.B.I. investigation into Hillary Clinton last year. Officials said it had nothing to do with the Russia investigation.
But the president undercut that argument a day later, telling NBC News, “When I decided to just do it, I said to myself — I said, you know, this Russia thing with Trump and Russia is a made-up story.”