House Intelligence Committee Chairman Devin Nunes appeared on “Fox & Friends” Tuesday, where he provided a potentially explosive hint at what’s driving his demand to see documents related to the Federal Bureau of Investigation’s Trump-Russia probe. “If the campaign was somehow set up,” he told the hosts, “I think that would be a problem.”

Or an understatement. Mr. Nunes is still getting stiff-armed by the Justice Department over his subpoena, but this week his efforts did force the stunning admission that the FBI had indeed...