President Trump’s firing of James Comey, the 7th director of the F.B.I., was an abuse of power. Republicans — Republican lawmakers and especially the congressional leadership — need to say so. But that is hardly enough.

Words must be followed by actions. At a minimum, Republicans must insist on a congressional select committee or independent commission to investigate Russian influence in the 2016 presidential election and any collusion between the president, his associates or campaign officials and Vladimir Putin’s Russia. What is now in the shadows needs to be brought into the light.

Among the reasons we can confidently conclude that the president abused his power is that the White House’s explanation for the expulsion of Mr. Comey was transparently false, even ludicrous. The reason the Trump administration gave for firing Mr. Comey this year is the exact same reason for which Mr. Trump praised Mr. Comey last year: the former F.B.I. director’s handling of the investigation into Hillary Clinton’s email server.

Based on his repeated public comments lacerating Mrs. Clinton and praising Mr. Comey for reopening the investigation in October, there is no disputing the fact that Mr. Trump personally rejects the core arguments that his aides are now giving for his firing of the F.B.I. director: that Mr. Comey overstepped his role; that he disclosed information critical of Hillary Clinton in July when the F.B.I. closed its investigation; and that he overstepped again when he reopened and re-closed the investigation right before Election Day. In fact, Mr. Trump’s animus toward Mrs. Clinton was so deep that he endorsed the “lock her up” chants from his supporters and declared that “she has to go to jail.”