After more than two years and the persistent goading of former president Donald Trump, special counsel John Durham, the lawyer Trump-era attorney general William P. Barr tapped to probe the Justice Department’s 2016 Russia investigation, finally did something on Thursday. He indicted attorney Michael Sussmann for allegedly lying to the FBI.

This, to put it mildly, is not the confirmation of some broad 2016 deep-state conspiracy against Mr. Trump that the former president apparently desired.

The danger of special counsel investigations is that, given unlimited time and resources, they often find some bad action tangentially related to their original inquiry that may have had little or no substantial negative impact. Mr. Durham has uncovered alleged wrongdoing that has little to do with whether federal officials tried to sabotage the Trump campaign.

The case against Mr. Sussmann is iffy. It revolves around a Sept. 19, 2016, meeting Mr. Sussmann had with James Baker, an FBI lawyer, in which Mr. Sussmann relayed concerns about curious Internet data that may have indicated that Mr. Trump, then a candidate for president, was in secret contact with Alfa Bank, a Russian financial institution. Mr. Baker claims that Mr. Sussmann said he was not representing any client during the meeting, when he was in fact working for the Hillary Clinton campaign. Mr. Sussmann denies he said that, and he argues that he was not technically representing the campaign during the meeting, anyway.

The indictment claims that had Mr. Sussmann informed the FBI of his ties to the Clinton campaign, they might have taken a different view of the information he presented. This is not the same as saying that investigators would have taken substantially different actions as a result. Indeed, the indictment admits that federal officials knew about Mr. Sussmann’s associations. Investigators would have examined the strange Internet traffic anyway, and dismissed the alleged Trump-Alfa Bank connection, as they did.

Even if true, the Sussmann episode is far less alarming than the case of former national security adviser Michael Flynn, whom Mr. Barr moved to protect from punishment and Mr. Trump later pardoned. Mr. Flynn admitted to lying to the FBI about his conversations with the Russian ambassador, an issue of central importance to the investigation of the Trump campaign’s connections to Russia. The consequences of Mr. Sussmann’s alleged lie are minimal by comparison.

The Justice Department indicated Thursday that Mr. Durham’s investigation is ongoing. So far there are no indications he has uncovered anything suggesting an illegitimate government plot to subvert the 2016 Trump campaign — or even that the Russia inquiry was unwarranted. That is because the facts already public proved long ago that there was ample reason for federal investigators to launch and pursue the Russia investigation. If Mr. Durham has nothing more compelling coming, he should bring an end to this long-running exercise.