Partisan fireworks exploded repeatedly between Republican and Democrat members of the House Select Committee on Benghazi during the marathon grilling that at times took on the character of an interrogation.
But the Democratic frontrunner for President was relentlessly composed as she accused her rivals of exploiting the deadly attacks in Libya - which came under her watch as Secretary of State - for political gain.
In her highly anticipated testimony, Clinton accepted - as she has done in the past - her share of blame for the attack which cost the lives of four Americans including ambassador Christopher Stevens. "I take responsibility for what happened in Benghazi," she said. "I'm here to honour the service of those four men."
The Benghazi tragedy has hovered over Clinton for three years, threatening to upend her White House candidacy, especially after the inquiry launched 17 months ago led to revelations that she used a homebrew email account and server while she was top diplomat.
Her strong performance at the hearing could help Clinton convince sceptical voters that it is time to move on from the controversy that has dogged her campaign.
Had she stumbled badly on such a consequential day, it would have invited enhanced scrutiny of her judgment and diplomatic acumen during the run-up to the November 2016 election.
Clinton, President Barack Obama's top diplomat from 2009 to 2013, warned against the "partisan agendas" that Democrats say are driving the Benghazi probe. "Let's be worthy of the trust the American people have bestowed upon us. They expect us to lead, to learn the right lessons, to rise above partisanship and to reach for statesmanship," she said in opening remarks.
There were several sharp exchanges with Republicans, including over the way the Administration first publicly characterised the attack - which came weeks before the 2012 presidential election - as a spontaneous reaction to an anti-Muslim video.
"Libya was supposed to be ... this great success story for the Obama White House and the Clinton State Department," conservative congressman Jim Jordan said in a fiery critique.
"You can live with the protest about a video. That won't hurt you. But a terrorist attack will," he said.
"Where did the false narrative start?" Jordan asked accusingly. "It started with you, Madam Secretary." Clinton rejected the charge, shooting back at Jordan: "I'm sorry that it doesn't fit your narrative, congressman."
The Benghazi committee has been deeply controversial and in recent weeks GOP lawmakers including number two House Republican Kevin McCarthy suggested that the panel served to help damage Clinton's standing in the presidential race.
Democrats have piled on, accusing Republicans of conducting a US$4.7 million ($6.9 million) witch hunt against Clinton.
"We're better than using taxpayer dollars to try to destroy a campaign," boomed the committee's top Democrat Elijah Cummings.
Congress has conducted seven probes into the Benghazi attack, and Clinton launched an Accountability Review Board to investigate the events.
The board's report did not fault the State Department but cited "systemic failures and leadership and management deficiencies at senior levels" that resulted in inadequate security.
Critics have pointed to the department's rebuff of requests for additional US security measures in Libya, left unstable after strongman Muammar Gaddafi's ousting.
Clinton insisted such requests, or rejection of requests, rarely reached her desk.
"None of them with respect to security in Benghazi did," she said.
