“What we are expecting to hear, in the secretary’s own voice, is the plan she has to reinvigorate and enhance diplomatic security services," he said. "What we are reminded of is how delicate the security situation is, and how attentively we need to stay focused.”

Will the Benghazi attack be a permanent and defining stain on Clinton’s tenure at the State Department? Former U.S. NATO Ambassador Robert Hunter does not think so.

“I do not think her image was at all tarnished by this. Secretary Clinton has set an incredible standard in the last four years in terms of America’s standing abroad, human rights, women’s rights,” Hunter said.

Republican Congressman Dana Rohrabacher agrees.

“She has given this country 20 years of decent, good service. And I am not about to sling mud at her. She maybe made a bad call. She has made 20 years of good calls.”

Hillary Clinton’s testimony on Capitol Hill precedes a Senate confirmation hearing for President Barack Obama’s pick to be America’s next secretary of state, Senator John Kerry.