An administration official said the combative nature of the hearing did not come as a surprise for a nominee who has faced more sustained and personal opposition than any of Obama's cabinet picks.
"There's no indication that this is peeling off any support that was there before today," said the official, who spoke on the condition of anonymity to discuss the administration's internal assessment.
The ranking Republican on the Armed Services Committee set the tone for the confirmation hearing for Hagel, a former Republican senator from Nebraska with a reputation for bluntness but also nuanced foreign policy views.
"Why do you think that the Iranian Foreign Ministry so strongly supports your nomination to be the secretary of defense?" Sen. James Inhofe (R., Okla.) asked Hagel, in an apparent reference to an Iranian news agency report conveying hope from the Islamic republic that Hagel's confirmation would bring "practical changes" in U.S. policy.
Hagel appeared defensive, frustrated, and lethargic during much of the hearing. But none of the zingers or missteps appeared serious enough to sway a significant number of senators to vote across party lines. Democrats outnumber Republicans on the committee 14 to 12, and administration officials and analysts said the vote would probably fall along party lines.
Hagel's nomination has triggered sustained criticism since his name was first suggested for the job in December. Previous remarks and votes on issues ranging from sanctions against Iran to the propriety of having an openly gay ambassador became fodder for a barrage of ads and an intense lobbying campaign that has sought to doom his nomination.
In his opening statement, Hagel defended his record, saying he always acted with integrity but acknowledging that it was not devoid of "mistakes." If he is confirmed, Hagel said, he would run the Pentagon guided by a long-held philosophy: "Is our policy worthy of our troops and their families and the sacrifices that we ask them to make?"
One of the first bruising lines of questioning came early, when Sen. John McCain (R., Ariz.) asked Hagel whether he regretted his opposition to the 2007 troop surge in Iraq.
"Were you right?" McCain asked sternly, eliciting a response that he seemed to find inadequate.
"I would defer to the judgment of history to sort that out," Hagel said.
Hagel faced relatively few nuanced questions about the Afghan war or terrorist threats. Afghanistan was mentioned just 27 times, and al-Qaeda only twice, while Israel got 178 mentions and Iran 169.
On Afghanistan, where 66,000 U.S. troops remain deployed, Hagel said he did not have enough knowledge about the war to have an informed opinion about the ideal size for the force the United States might leave behind after its combat mandate expires at the end of 2014.
Senators spent a great deal of time pressing Hagel on his views on Iran, demanding to know why he has in the past rejected unilateral sanctions and why he refused to endorse an effort to designate the Iran's Revolutionary Guard a terrorist organization.
The question elicited one of Hagel's most damaging missteps, as he argued that it would have been unprecedented to add a military unit of an "elected, legitimate government" as a terrorist organization. Senators took exception to that characterization, which Hagel later softened.
Hagel struggled when Sen. Lindsey Graham (R., S.C.) asked him to expand on his past assertion that the Israeli lobby "intimidates a lot of people" and challenged him to point to a single senator who feels intimidated. "Name one," Graham said, eliciting a meek response from Hagel, who said: "I do not know."