WASHINGTON—The day in three images: Hillary Clinton delighted, laughing and nodding. Hillary Clinton disdainful, her cheek resting in her hand. A couple sitting in the public seating area, fast asleep.

Clinton, the Democratic presidential candidate and former secretary of state, testified over the course of 11 hours Thursday before the Republican-led House of Representatives committee that is conducting yet another investigation into the 2012 terrorist attack on a U.S. diplomatic compound in Benghazi, Libya.

The committee, supposedly a neutral fact-finding body, is now viewed by most of the country as a partisan weapon for undermining Clinton. On this day, it couldn’t even do that.

Clinton, calm and prepared, airily brushed aside a disjointed series of questions that veered from her role in advocating the failed war in Libya to her friendship with political operative Sidney Blumenthal. Seven hours in, even Fox News, leading purveyor of Benghazi conspiracy theories, was bored or sad enough to switch to regular programming.

Clinton was winning.

“As somebody who’s been both a witness and a counsel, this is a textbook example of how to be a good witness,” John Dean, former counsel to president Richard Nixon, said on MSNBC.

The last time Clinton faced a congressional grilling on the Benghazi attack, in 2013, she eventually offered up an exasperated comment — “What difference, at this point, does it make?” — that wound up as fodder for conservative attack ads. Her marathon testimony this time is more likely to appear in an ad of her own.

“I’ve thought more about what happened than all of you put together,” she said. “I’ve lost more sleep than all of you put together.”

The attack killed U.S. Ambassador Chris Stevens, a second diplomat and two CIA contractors. As they have for three years, Republicans criticized the Obama administration’s mistaken post-attack claim that the violence was provoked by an anti-Muslim video, rather than terrorism, and accused Clinton of negligence in failing to provide adequate security to the diplomats.

They also attempted to defend themselves. The committee’s credibility has been severely undermined by the comments of two Republicans who have acknowledged that its aim is to tarnish Clinton’s candidacy.

“Madam Secretary, I understand there are people, frankly, in both parties who have suggested that this investigation is about you. Let me assure you, it is not,” said Representative Trey Gowdy, the committee chairman. “This investigation is about four people who were killed representing our country on foreign soil.”

His claim was weakened by the tangents of his colleagues. Nearly 10 hours in, Representative Jim Jordan began interrogating Clinton about her emails. Earlier, Representative Peter Roskam accused Clinton of trying to hog the glory for the toppling of Libyan dictator Moammar Gadhafi.

“Let me tell you what I think the Clinton Doctrine is,” Roskam said. “I think it’s where an opportunity is seized to turn progress in Libya into a political win for Hillary Rodham Clinton.”

Clinton’s big October

Her poll numbers were falling fast. Her email scandal was consuming her message. The media had pulled its Clinton-in-disarray narrative out of long-term storage. And then, with the help of three big developments, her campaign turned itself around.

Republicans’ self-inflicted wound: Democrats believed the Benghazi committee was a witch hunt. Republicans had insisted they were just looking for the truth. In late September, a top Republican inexplicably abandoned the party line.

“Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee, a select committee. What are her numbers today? Her numbers are dropping,” House Majority Leader Kevin McCarthy said.

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Debate domination: The first Democratic debate, last week, was Bernie Sanders’s big chance to introduce himself to a national audience. It turned into Clinton’s shining reintroduction. Polished, aggressive and conversational at once, she seemed nothing like the defensive schemer of recent email-focused interviews. She gained an average of six points in national polls.

Biden bows out: A Joe Biden candidacy would have made the battle for the nomination far more complicated. When the vice-president announced Wednesday that he would not be running, he turned the race into a simple two-candidate showdown — liberal versus “democratic socialist,” party titan versus lifelong outsider — that Clinton far preferred to a three-way scrap involving another Democratic heavyweight.