Washington, AP/Reuters—Democratic presidential contender Hillary Rodham Clinton is taking center stage as the star witness in the Republican led investigation into the deadly 2012 attacks in Benghazi, Libya.

The Democratic front-runner for president goes before the panel on Thursday with newfound political strength. A potential rival for the nomination, Vice President Joe Biden, announced on Wednesday he will not jump into the presidential race.

Even so, Clinton faces a formidable challenge, as she tries to explain security lapses at the US diplomatic compound in Benghazi while she was secretary of state. This is Clinton’s second appearance before Republican-dominated Congress on her handling of the incident.

Clinton is expected to explain security lapses at the US diplomatic compound in Benghazi, the slow military response to the violence and the Obama administration’s changing narrative about who was responsible for the attacks that killed four Americans, including US ambassador Chris Stevens, and why the attacks were launched.

Clinton also is certain to face questions about her use of a private email account and server while serving as secretary of state in a high-stakes, day-long appearance that could solidify her hold on the Democratic nomination or raise doubts about her candidacy.

The committee also faces a “make or break” moment.

The hearing comes amid an escalating partisan feud on the 12-member committee, which has spent more than 4.5 million dollars since its creation in May 2014.

The panel’s chairman, Republican Trey Gowdy of South Carolina, and other Republican investigators know their questioning of Clinton could revive the beleaguered panel’s credibility or see it sink further.

Democrats have complained about “selective and out-of-context leaks” that they said “mischaracterized” testimony by top Clinton aides and other witnesses. They say the panel has devolved into partisan harassment intended to hurt Clinton’s bid for president.

Gowdy and other Republicans say the panel has been and remains focused on those killed in Benghazi and on providing a definitive account of the attacks. There have been seven previous investigations. “This has never been political for us,” said Republican Martha Roby, a member of the Benghazi panel. “This has always been about finding out the truth”.

“I’m looking forward to answering questions about the real things when I’m there,” Clinton said in a television interview earlier this month. She voiced disgust at what she said were Republican admissions that “it’s a political partisan committee for the sole purpose of going after me.”