Never look a gift horse in the mouth, as the old saying goes, especially if that gift horse is a scathing critique of Hillary Clinton’s incompetence on national security, delivered by one the nation’s top-ranking law enforcement officials. But House Republicans, outraged over the fact that F.B.I. director James Comey declined to recommend charges be brought against the former secretary of state, did just that Thursday, undermining a ready-made attack ad by grilling the same man who was set to deliver it.

Within hours of Comey’s press conference Tuesday announcing that his agency was not recommending an indictment over Clinton’s use of a private e-mail server and her handling of confidential information while serving as secretary of state, congressional Republicans immediately summoned the F.B.I. director to appear before a House Oversight Committee hearing to explain his decision. What followed was something akin to a kangaroo court, during which the Republicans on the committee continually pressed Comey, a former Republican who left the party when he became the Bureau’s director,to admit that he was a Clinton pawn.

“I’m not a conspiracy theorist but I have some questions about how this came down,” Rep. John Mica said, insinuating that Comey had illegally coordinated with the Clinton campaign. Comey, who just two days earlier had unleashed a string of blistering comments about Clinton’s feckless approach to cyber-security issues, was not amused. “Look me in the eye, and listen to what I have to say: I did not coordinate that with anyone,” Comey replied, his composure cracking for the first time during the hours-long hearing. “The White House, the Department of Justice, nobody outside the F.B.I. family had any idea what I was about to say. I say that under oath. I stand by it . . . I don’t mean to get strong in responding, but I wanted to make sure I was definitive about that.”

Pushed by other Republicans on the House committee to defend himself, Comey was forced to explain in greater detail all the reasons Clinton’s actions were not prosecutable, blunting the F.B.I. director’s earlier criticism. “No Justice Department, whether under Democrats or Republicans, would prosecute that case,” he said flatly at one point, describing how Clinton’s negligence did not amount to criminal wrongdoing. Pressed again and again, Comey repeatedly stated that only once in 100 years did the federal government bring charges against someone for mishandling classified information. He dryly told an outraged committee-member that he did not make Clinton testify under oath because it was already a crime to lie to the F.B.I. One congressman could not fathom the differences between state laws and the federal law that did not allow Comey to prosecute Clinton. Committee Chairman Jason Chaffetz even tried to get Comey to admit that he was favoring Clinton by not nailing her for running her e-mails by outside lawyers. (“I think it would be a very tall order [to prove] she was acting with criminal intent,” Comey noted.)

Democratic Rep. Elijah Cummings, meanwhile, a panel-member who has been a frequent critic of the G.O.P.-controlled House Oversight Committee, condemned the hearing as a witch hunt. “Amazingly, amazingly, some Republicans who were praising you just days ago for your independence, for your integrity, and your honesty, instantly turned against you, because your recommendation conflicted with the predetermined outcome they wanted,” Cummings said. “In their eyes, you had one job. And one job only: to prosecute Hillary Clinton. But you refused to do so. So now you are being summoned here to answer for your alleged transgressions. And in a sense, Mr. Director, you are on trial.” (Rep. Stacey Plaskett suggested that Comey’s time would be better spent looking into the past week’s spate of fatal police shootings of black men.)

While it’s certainly painful to see the Republicans drop the ball in this round, it was unsurprising, even inevitable that they would turn what might have been a natural political alliance with the F.B.I. into another conspiracy-fueled imbroglio. After all, this is the same committee that has launched eight separate investigations into the 2012 Benghazi attack, including one last year in which Clinton was grilled for some 11 hours. And from the looks of it, the House Oversight Committee is not done trying to find some way to officially label Clinton a crook: just hours after Comey concluded his testimony, Rep. Chaffetz confirmed to MSNBC that he would ask the F.B.I. for a new​ investigation, this time examining whether Clinton had lied to Congress about her e-mail use. Maybe, this time, something will stick.