Special counsel Robert S. Mueller III leaves a closed-door meeting on Capitol Hill on June 21, 2017. (J. Scott Applewhite/AP)

Philip Allen Lacovara is a former president of the D.C. Bar. He served as counsel to the Watergate special prosecutor.

Last week’s lengthy report by the Justice Department’s inspector general on former FBI director James B. Comey’s actions during the Hillary Clinton email investigation illustrates the grave risks of making law enforcement announcements on the eve of an election. It also offers a lesson to special counsel Robert S. Mueller III: It’s time to act on the remaining pieces of his investigation into possible collusion between the Trump campaign and Russian officials.

There is little time for delay. To ensure that the investigation does not tilt the scales in the November midterm elections, Mueller should promptly return any indictments that the evidence warrants. Any hurdles preventing this from happening soon — such as sparring with the president and his legal team over obtaining his testimony — should be eliminated from the calculus.

I strongly support both the need for a vigorous, independent investigation and the professionalism of Mueller, and I have no interest in encouraging him to abandon his investigation prematurely. But it seems that the special counsel should have enough information now to decide whether there is a basis for filing any more Russia-related charges than already have been filed.

Mueller was appointed to conduct this investigation almost 13 months ago. Although he has obtained guilty pleas from several figures and indicted a couple of campaign officials, as well as more than a dozen Russian individuals and companies, the central issue remains unresolved: To what extent did President Trump and his campaign actively conspire with the Russians to influence the election?

A comparison with the Watergate special prosecutor’s investigations is illuminating. The special prosecutor was assigned five distinct areas to probe, including most notably the responsibility for the Watergate break-in at Democratic National Committee headquarters and for the ensuing  coverup. His team also investigated the aftermath of the Pentagon Papers leak, the conduct of “dirty tricks” during the 1972 presidential campaign and the pattern of violations of campaign finance restrictions.

Yet, within 10 months following Archibald Cox’s appointment, and despite his intervening firing in the Saturday Night Massacre, Cox’s successor, Leon Jaworski, was able to achieve indictments of all principal players in the Watergate coverup, as well as in all other areas of inquiry — and to have the grand jury name the president an unindicted co-conspirator. Those cases were solidly prepared within that period, and almost all the defendants were promptly convicted.

One loose end seems to be dragging on the pace of Mueller’s inquiry: possible testimony from Trump. If disputes with Trump’s team about whether he will appear voluntarily are delaying the conclusion of the investigation, it’s best not to pursue Trump’s testimony.

Trump’s testimony is like the gag from Charles Schulz’s “Peanuts” comic strip. Time and again, the White House promises Mueller that it will allow him to kick the football but then yanks it away at the last second. Trump and his tag team of lawyers regularly assure that the president is willing to cooperate, but his lawyers also worry that Trump could be lured into a “perjury trap” if he were to cooperate. As the latest presidential lawyer, Rudolph W. Giuliani, recently conceded, the president’s “recollections keep changing.”

The chance that Trump actually will submit to an interview voluntarily, much less provide testimony under oath, is vanishingly small. So the issue is whether Mueller should subpoena Trump to force his testimony. Trump’s lawyers contend that the president is not even subject to such a subpoena, a position that seems impossible to square with the unanimous Supreme Court decision in 1974 enforcing the subpoena to President Richard M. Nixon that required him to supply evidence despite his claim of executive privilege.

Nevertheless, Trump and his lawyers would bitterly contest any subpoena, setting the stage for a time-consuming “constitutional confrontation” that would delay Mueller’s investigation and extend into the autumn election season.

If testimony from Trump were essential to finding out what happened, this confrontation might be worth it. But it is not. In Watergate, we explained to the Supreme Court that access to the Nixon tapes was crucial to determining whether White House counsel John Dean’s testimony was accurate in identifying the roles of various White House aides, and Nixon himself, in the Watergate coverup. The tapes were undeniably reliable, contemporaneous evidence.

But who really believes that testimony from Trump would illuminate the truth? Any resemblance between the president’s statements and the facts would be purely coincidental. Sadly,  no responsible prosecutor could rely on Trump’s testimony either to exonerate a suspect or to convict one.

Would it seem unfair to Trump and his aides, or to the country, to pass up the inevitable fight over compelled testimony? I think not. Trump and his allies could hardly complain about indictments (or a report) without Trump’s views, if the president himself refuses to provide his version of the “alternate facts.” For the rest of the country, the president’s unreliability as a witness would render his absence from the formal record essentially meaningless.