But two Republican senators, McCain and Ron Johnson of Wisconsin, raised the Benghazi issue at the hearing Thursday.

Johnson on Wednesday had grilled Clinton about the erroneous initial talking points used to explain the cause of the attack to the public. While it was first said the attack was a spontaneous protest over an anti-Islamic film, the administration later defined the violence as a planned terrorist attack.

"With all due respect, the fact is we had four dead Americans," Clinton said in response to Johnson's repeated questions. "Was it because of a protest or was it because of guys out for a walk one night decided they'd go kill some Americans? What difference, at this point, does it make? It is our job to figure out what happened and do everything we can to prevent it from ever happening again, senator."

Republicans have made the phrase "what difference ... does it make" a talking point, and Johnson seized on it Thursday.

"I think it makes a big difference whether or not the American people have the confidence that the president and the administration is being truthful with them," he said. "So, I guess my question is do you agree with that point? Are you willing to work with me or do you basically kind of agree with Hillary Clinton that that's kind of yesterday's news and let's move on."

But Kerry told Johnson that if he was attempting to "get some daylight between me and Secretary Clinton, that's not going to happen here today."

He offered the possibility that the senator and Clinton are "talking past each other."

"I don't think that was the question," Kerry said. "I think that if your question is, should the American people get the truth and does it matter, Hillary Clinton would say yes and I say yes, but that's not what I think she was referring to. I think what she was referring to was sort of the question of, you know, the sequencing and the timing of how particular information came in with respect to the talking points and the public statements that were made.

"And there was a difference of opinion, in my judgment, as to how you saw that versus how she saw that."

Kerry's stellar reputation

Kerry, the 2004 Democratic candidate for president defeated by President Bush, is noted for having the experience, gravitas and relationship-building skills that could help him as Clinton's successor.

He has traveled the globe on behalf of the Obama administration to mend frayed relationships. Most notably, he traveled to Pakistan amid deteriorating relations from a series of incidents, including the raid that killed al Qaeda leader Osama bin Laden.

Obama has praised the senator's "extraordinarily distinguished Senate career" and military service in the Vietnam War. He said Kerry has earned the respect and trust of his Senate colleagues, both Democrats and Republicans, and the president said he's confident the Senate will swiftly confirm the nomination.

Others have echoed the praise for Kerry.

"There are very few people with greater experience over a longer period of time," said Nicholas Burns, a former career ambassador who has served every secretary of state since Warren Christopher, and was most recently undersecretary for political affairs under Condoleezza Rice. "He would be a very, very impressive choice."

"You really need someone who is a renaissance person with a tremendous range of skill, both political and substantive, with a deep reservoir of knowledge," Burns said. "You need someone who can drill several layers deep on foreign policy issues."

Kerry, 69, spent much of his childhood overseas. After graduating from Yale University in 1966, he was deployed to Vietnam as a lieutenant in the U.S. Navy. He was a gunboat officer on the Mekong Delta, earning the Silver Star, the Bronze Star and three Purple Hearts.

Upon his return home in the early 1970s, Kerry gained public recognition as the head of the group Vietnam Veterans Against the War and for his anti-war testimony before the Senate Foreign Relations Committee.

In 1972, he ran his first campaign, a losing effort for a congressional seat in Massachusetts. In 1982 he became lieutenant governor under Massachusetts Gov. Michael Dukakis. Two years later, Kerry won the U.S. Senate seat he has held for five consecutive terms.

Kerry would come to the secretary of state post with a full plate of foreign policy hot spots, including the civil war in Syria, the nuclear antics of North Korea, a looming showdown with Iran over its nuclear program, political chaos in Egypt and the rest of North Africa, and, of course, the Middle East peace process.

Like Obama, Kerry sees the benefit of reaching out to adversaries, like Iran and Syria, and giving them a chance to negotiate. At one point, Kerry spearheaded outreach efforts to Syrian President al-Assad before the administration turned on al-Assad because of his crackdown on protesters.

But he also has called for arming the Syrian opposition and for NATO airstrikes, which Obama's administration has resisted.