The attorney general of the United States has concerns about illegal government spying.

At a Senate hearing on Wednesday, William Barr confirmed that he will look into whether the Trump campaign was subject to unlawful surveillance in the run-up to the 2016 election. The Justice Department’s inspector general, Michael Horowitz, is already investigating the matter, and Mr. Barr says the review is nearly done.

But instead of letting his watchdog finish his work, Mr. Barr would rather look into the matter himself. “Yes, I think spying did occur,” Mr. Barr said early in the hearing, later amending the record to clarify that he was “not saying that improper surveillance occurred.”

“I am saying that I am concerned about it and looking into it. That is all,” he added.

Before day’s end, Fox News was amplifying the attorney general’s worries, which the president then shared on Twitter.

Whatever comes of Mr. Barr’s review and the conspiracy theories that ensue, he would be wise to reflect on his own history with government surveillance that stretched the limits of the law. Just last month , Mr. Horowitz’s office concluded that the Justice Department and the Drug Enforcement Administration “failed to conduct a comprehensive legal analysis” when the two agencies undertook a secret surveillance program in the 1990s that swept up records of Americans’ phone calls — the kind of bulk collection that the National Security Agency later engaged in after 9/11.