To watch Hillary Clinton’s Republican antagonists during Thursday’s public hearing of the House Select Committee on Benghazi was to wonder how they could possibly behave the way they did. As representatives of the American people, they not only failed miserably to fulfill the responsibilities entrusted to them, but exposed their own blithering ignorance of basic aspects of government.

Determined as they were to encourage doubt about Clinton’s presidential candidacy, they instead elevated her and raised hard questions about their own knowledge, character, temperament, and intellectual capacity to serve in Congress. After months of “investigating” Clinton, the Republican committee members have developed only a dim understanding of simple phenomena — like the many and varied sources of information, beyond emails, that are available to the Secretary of State. Only someone very dense, very poorly informed, or both, would believe, for instance, that she had received “most of her intelligence about Libya,” or any other subject, in unclassified email traffic.

Often the sheer mindlessness of their inquiries was stunning: Rep. Martha Roby (R-AL) asked Clinton whether she had been alone “all night” at home on Sept. 11, 2012, while the tragic events in Benghazi occurred. Rep. Mike Pompeo inquired whether the late Ambassador Chris Stevens had ever visited Clinton’s home or possessed her “fax number.” Rep. Peter Roskam (R-IL) demanded that Clinton admit that as Secretary of State she had overseen American policy toward Libya. Several of the Republicans interrupted her rudely, upbraided her for looking at notes, even while they read from their own notes, and demanded that she give “Yes or No” answers to their queries, as if they were prosecutors grilling a perp.

The lines of inquiry that the Republicans pursued were muddled, directionless, and confusing, seemingly even to them. As the Democrats repeatedly pointed out, after all the tumult over Clinton’s emails, the proceedings of this committee so far — following several legislative and administrative investigations — revealed nothing new about the terrorist attack on the US compound in Benghazi, its prelude, or its aftermath.

So what might American taxpayers have gleaned from those 11 hours of hearings, the culmination of an expenditure of 17 months and $4.8 million? They learned that Rep. Trey Gowdy (R-SC), the committee chair, is obsessed with someone named Sidney Blumenthal, a friend of Clinton who sent her emails about Libya and other topics. He’s not just weirdly preoccupied, as anyone could see, but truly obsessed to the point of choking rage.

Those who have followed Gowdy’s conduct during the months leading up to this moment will find this Blumenthal business all too familiar. Having discovered that Blumenthal sent some emails to Clinton about Libya, largely incorporating information he had gathered from retired intelligence personnel, the chairman and his colleagues sought to fabricate a conspiracy theory of the Benghazi attack that somehow involved him.

Actually, “conspiracy theory” is too coherent a description of their aimless maundering on the topic of Sidney (who also happens to be my friend).

Gowdy appeared to believe – or perhaps pretended to believe – that if only the Secretary of State had ignored Blumenthal’s emails, the Benghazi attack might somehow have been prevented. According to this theory, she was paying too much attention to him, and not enough to Stevens.

In fact, as Clinton patiently attempted to explain over and over, she naturally delegated decisions about the safety of the Benghazi compound and personnel — and all perilous diplomatic posts — to the State Department’s security staff. Moreover, her communications with Blumenthal were, and are, entirely irrelevant to the matters that Gowdy purports to be investigating. Should Gowdy ever really wish to know why it is difficult to protect our embassies, consulates, and foreign service officers abroad, he might investigate himself and all the other Republicans who – as Rep. Jason Chaffetz (R-UT) acknowledged on Thursday – voted repeatedly to slash hundreds of millions of dollars from the State Department’s security budget.

As I noted in Politico months ago, back when Gowdy first embarked on the Blumenthal trail, this isn’t the first time that the former Washington Post and New Yorker journalist has driven Republican politicians to manic distraction. Like Clinton herself, he is a demonized figure in certain circles – but every time they go after him, they risk humiliation or worse.

Among the many low points of the Clinton hearing was the moment when Gowdy first refused a committee vote on releasing Blumenthal’s deposition before the committee, and then whipped a party-line vote to keep it under seal. Rep. Elijah Cummings (D-MD), the ranking member who led his fellow Democrats in eloquently protesting the committee’s many abuses, asked Gowdy what he is hiding.

But of course Cummings already knows the answer: In that closed deposition last June, Gowdy and company asked Blumenthal dozens of questions about wholly irrelevant but highly political matters, such as his employment by the Clinton Foundation, Media Matters, and Correct the Record – even though Gowdy has publicly claimed that he had no interest in those subjects. To release Blumenthal’s testimony would risk exposing the committee chairman’s bad faith and clumsy deceptions.

By the time Rep. Trey Gowdy finally gaveled the hearing to a close, there was little doubt that Hillary Clinton’s composed, dignified demeanor – and the contrast between her and the Republicans — had notched another political victory for her. She had movingly recounted the events of that awful night in Benghazi, explained her actions in detail, firmly defended the honor of Accountability Review Board chairs Tom Pickering and Admiral Mike Mullen, and pleaded for a return to statesmanship. Her strong performance rallied skeptical liberals to her side, while furious conservatives whined in despair.

And when it was over she rose from the witness chair, smiling and greeting friends, while Gowdy stalked out, stone-faced and perspiring, as if he had seen his own demise.