WASHINGTON — Chuck Hagel, President Obama’s nominee as defense secretary, confronted withering criticism during a marathon confirmation hearing Thursday, but administration officials said they felt confident that the Republican-led attacks did not derail his bid to lead the Pentagon.
Lawmakers from both parties spent roughly eight hours grilling Hagel about remarks he has made at various points of his career and the votes he had cast in the Senate. The nominee at times struggled as he sought to explain his past positions, in some cases distancing himself from them. But he offered a full-throated endorsement of the United States’ alliance with Israel, insisted that he has never advocated for unilateral nuclear disarmament, and called Iran an existential threat.
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.
The ranking Republican senator 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?’’ Senator James Inhofe of Oklahoma asked Hagel, in a reference to an Iranian news agency report conveying hope that Hagel would bring ‘‘practical changes’’ in US policy.
Hagel appeared defensive, frustrated, and lethargic during much of the hearing. But none of his 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.
‘‘None of the votes that probably would have been for him have shifted,’’ said Steve Clemons, a fellow at the New America Foundation who supports Hagel’s nomination. But he expressed surprise by the lack of charisma Hagel displayed.
‘‘Hagel, who can be hilarious, didn’t show much of that today,’’ Clemons said.
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.
During 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 when Senator John McCain, an Arizona Republican, 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, refusing repeatedly to provide a yes-or-no answer.
Hagel later said that the Iraq war, including the surge, was the ‘‘most fundamentally bad, dangerous decision since Vietnam.’’
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 US 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. He agreed with a senator’s characterization that Obama intends to draw down troops ‘‘sooner rather than later.’’
‘‘I think he’s made that very clear,’’ Hagel said. ‘‘If I am confirmed, I will need to better understand all the dimensions of this.’’
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 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. On the broader question of the best approach to reducing the threat Iran poses, the nominee defended some of his past positions.
‘‘I think it’s always wise to try to talk to people before you get into war,’’ he said. He later added: ‘‘I never thought engagement is weakness.’’
Hagel was also challenged about a comment he made in a newspaper interview in August 2011, in which he was quoted as saying that the Pentagon’s budget was bloated. On Thursday, he said he had made the comment before Congress passed a bill that imposed substantial defense cuts. The interview was, in fact, conducted after the bill’s passage.
The nominee said he would run the Pentagon in a fiscally responsible manner and rejected the assertion that he favors the congressionally mandated across-the-board cuts that could kick in March 1 if the White House and Congress fail to reach a deal on debt reduction.