Pete Hegseth, President-elect Donald J. Trump’s pick to lead the Pentagon, sought to defend himself against a raft of criticism during a confirmation hearing on Tuesday, as Democrats pressed him on his views about women in combat and support for convicted war criminals. Mr. Hegseth also claimed to have been the victim of a “smear campaign” that raised allegations of past misconduct.

But a key Republican member of the committee, Senator Joni Ernst of Iowa, a veteran and a sexual assault survivor, appeared satisfied with his responses to her questions about the role of women in the military and sexual assault prevention. Ms. Ernst, who is seen as critical to Mr. Hegseth’s confirmation chances, spent much of her time focusing on their agreement that the Pentagon should be audited.

The tense hearing opened with Senator Jack Reed of Rhode Island, the top Democrat on the committee, saying that he believed Mr. Hegseth was not qualified to serve as defense secretary, adding that accusations against him, which include an allegation of sexual misconduct and episodes of drinking to excess, were “alarming.”

After his opening remarks, which were repeatedly interrupted by hecklers, Democrats quickly began grilling Mr. Hegseth about his statements that the military’s standards had been lowered to accommodate women and his advocacy for pardons for soldiers convicted of war crimes.

Mr. Reed pressed Mr. Hegseth about his advocacy of pardons for such soldiers, prompting him to claim that the country’s rules of engagement were “restrictive” and that military attorneys had put their own promotions ahead of “having the back” of troops in combat.

And in response to questions from Senator Jeanne Shaheen, Democrat of New Hampshire, about his view of women in the armed forces, Mr. Hegseth claimed without evidence that there has been an erosion of “standards” in the military, but vowed that women would be treated well under his watch. His response did not impress Ms. Shaheen: “I appreciate your 11th-hour conversion,” she said.

It remains unclear whether Mr. Hegseth has the votes to be confirmed. After the committee hearing, the full Senate must vote on the confirmation. If all Senate Democrats oppose him, he can afford to lose the support of just three Republicans in the chamber.

Accusations: The New York Times and other news organizations have documented a pattern of excessive drinking by Mr. Hegseth. In the most serious allegation against him, a woman in Monterey, Calif., accused him of raping her in 2017. Mr. Hegseth said the encounter was consensual, and it resulted in no criminal charges. His lawyer said Mr. Hegseth was inebriated at the time.

Background check: The top members of the Senate Armed Services Committee were briefed late Friday on the F.B.I.’s background check of Mr. Hegseth. Others suggested that they might not have all the information they need about him. Senator Tammy Duckworth, Democrat of Illinois, has said she wants to see the F.B.I. background check and Mr. Hegseth’s financial disclosures, and wants to know about “any other allegations he might be facing.”

Leadership questions: Mr. Hegseth, who has been married three times, has also acknowledged having extramarital affairs. Extramarital affairs and public intoxication can leave officers and troops in the military subject to disciplinary action. Some senior military leaders have questioned privately whether Mr. Hegseth’s confirmation could send conflicting messages to troops about discipline.

Past commentary: Mr. Hegseth’s commentary and writings on a number of issues are also likely to come up. In his book “The War on Warriors: Behind the Betrayal of the Men Who Keep Us Free,” Mr. Hegseth complained about “woke” generals who he said had made the military “effeminate” by pushing diversity policies.

Women’s roles: Before Mr. Trump picked him, Mr. Hegseth had said that he did not believe women should be in combat. He has since offered some clarification. “If we have the right standard and women meet that standard, roger — let’s go,” he said on “The Megyn Kelly Show” podcast. “If they can’t, and that’s a product of physical differences because the standard is high, then that’s just the reality.”

Sharon LaFraniere and Dylan Freedman contributed reporting.

In response to a recitation of the many allegations of personal misconduct that have been made against Hegseth, the nominee said: “I have failed in things in my life, and thankfully I’m redeemed by my lord and savior Jesus.” Falling back on religious claims of redemption appears to be Hegseth’s main line of defense for himself rather than offering substantive denials.

Senator Tim Kaine, Democrat of Virginia, refuted Hegseth’s characterization that the charges against him were anonymous. “You claim that this was all anonymous? We have seen records with names attached to all of these, including the name of your own mother,” Kaine said, adding: “So don’t make this into some anonymous press thing.”

Senator Tim Kaine asked about allegations from former colleagues who claimed that he drank excessively, his admitted extramarital affairs and the sexual assault allegation. Hegseth vigorously denied the allegations but also refused to say whether that behavior would be disqualifying for a defense secretary.

Hegseth has repeatedly said that he was “completely cleared” by a police investigation into an accusation that he raped a woman in Monterey California in 2017. In fact, the police referred the case to the prosecutor’s office, and prosecutors declined to charge him. That is not the same as being completely cleared.

Senator Tim Kaine is focusing on Hegseth’s history of adultery, asking if he would respect his oath of office as defense secretary the same way he did for his marriage vows to his first and second wives.

Early in the hearing, Hegseth said that people who had positive things to say about him were ignored by the news media. But this New York Times article on his views over time about soldiers who were charged with war crimes quotes several people who served with and admired Hegseth.

Hegseth says troops will “rejoice” if the Pentagon gets rid of the “woke” agenda. Some 43 percent of the 1.3 million men and women on active duty in the United States military are people of color.

Hegseth: “One of the least racist institutions in our country is the military.” But until Lloyd Austin became secretary of defense in 2021, only white men led the Pentagon.

Hegseth refuses to say whether he would direct U.S. forces to invade Greenland if the president ordered military action against the island, which is part of Denmark — a NATO ally.

Senator Mazie Hirono also asked Hegseth if he would commit to resigning if he drinks on the job as secretary of defense. Hegseth said, “I’ve made this commitment on behalf of the men and women I’m serving” - an apparent reference to his promise that he would not let a drop of liquor pass his lips if he is confirmed. He doesn’t answer whether he would resign if he breaks that promise.

Hegseth’s pledge to abstain from alcohol echoed that of another nominee for defense secretary, John Tower, who in 1989 said: “If confirmed, I won’t have a drink.” Tower also promised to resign if he faltered, but it still was not enough to overcome his reputation of being a carouser and the Senate voted him down.

Senator Mazie Hirono of Hawaii is the first Democratic senator on the panel to use her question time to directly query him about allegations of sexual assault and alcohol abuse.

Ernst used her time to get Hegseth to repeat publicly promises she had previously said he made to her in private: to support the role of men and women in the military provided they can meet certain standards, to appoint a senior officer to strengthen her past work to prevent sexual assault and rape in the military, and to conduct an audit of the Pentagon.

Senator Joni Ernst urges Hegseth, if confirmed, to stress that “every man and woman has opportunity to serve their country in uniform and do so at any level as long as they are meeting the standards that are set forward,” adding that she believes in high standards. Hegseth said he would support that with the caveats she articulated.

Ernst noted that she was denied the opportunity to serve in combat because of her gender while in the Army.

Nearly two hours into his Senate hearing, Pete Hegseth, President-elect Donald Trump’s choice to be defense secretary, has vigorously defended himself on a range of contentious issues, including a sexual assault allegation, his lack of management experience and his comments against women serving in combat.

In his opening remarks, Mr. Hegseth hinted at his disdain for the Pentagon’s diversity, equity and inclusion programs, saying “our standards will be high and they will be equal — not equitable.”

Instead, Mr. Hegseth, an Iraq and Afghanistan combat veteran, presented himself as the “warrior” he has accused the left of targeting. He said he would “return the Pentagon back to warfighting” and “restore the warrior ethos back to the Pentagon.”

Senator Tom Cotton, an Arkansas Republican, gave Mr. Hegseth the opportunity to clarify his many past public comments about women not belonging in combat in the military. Mr. Hegseth said that when he said that, he meant standards, and added that: “What is true is that the weight of the ruck on your back doesn’t change.”

“Whether it’s a man or a woman,” he said, “they have to set the same high standards.”

Mr. Hegseth has not directly addressed an accusation that he sexually assaulted a woman in 2017 or has a history of excessive drinking. Instead he has heatedly blamed the media for circulating allegations from anonymous sources that he says are false. Previously he has denied the assault allegation, which did not lead to criminal charges.

Republican and Democrats have so far followed partisan lines for Mr. Trump’s pick.

In his opening remarks, Senator Roger Wicker, Republican of Mississippi and the chairman of the committee, spoke about the failures of past civilian leaders of the Pentagon, opining that Mr. Hegseth’s military experience and “unconventional” background “may be what makes Mr. Hegseth an excellent choice.”

Mr. Hegseth does not the fit the mold of most former defense secretaries — former generals, C.E.O.s and lawmakers — and said that was an asset. “As President Trump also told me, we’ve repeatedly placed people atop the Pentagon with supposedly the right credentials, whether they’re retired generals, academics or defense contractor executives. And where has it gotten us?”

Senator Jack Reed of Rhode Island, the top Democrat on the Armed Services Panel, told Mr. Hegseth in his opening remarks that he was unqualified to lead the Pentagon.

“Indeed, the totality of your own writings and alleged conduct would disqualify any service member from holding any leadership position in the military, much less being confirmed as the Secretary of Defense,” Mr. Reed said.

Senator Reed said that Mr. Hegseth is woefully short on managerial experience, noting that two small nonprofit veterans groups he ran ended up in debt. “I don’t know how he’s going to run an organization with an $857 billion budget and 3 million individuals,” he said.

The packed hearing room on Capitol Hill was disrupted early on three times by hecklers opposing Mr. Hegseth. Capitol Police quickly hustled out the shouting protesters.

Blumenthal asked Hegseth repeatedly if he would agree to an expanded F.B.I. background check. Hegseth dodged, saying he wasn’t in charge of background checks. Democrats have criticized the background check as insufficiently thorough. According to several sources, the F.B.I. did not conduct a substantive interview of one of Hegseth’s ex-wives last week despite the fact she called the bureau repeatedly to try to set it up.

“I would support you as the spokesperson for the Pentagon, I don’t dispute your communication skills,” Senator Richard Blumenthal, Democrat of Connecticut, as he argues Hegseth doesn’t have the management experience necessary to be defense secretary.

Senator Joni Ernst, Republican of Iowa, kicks off her testimony by submitting a letter from Hegseth’s successor at Concerned Veterans of America, praising his leadership skills. Ernst has not said yet whether she will vote for Hegseth, though she committed to support him going through the Senate’s confirmation process.

“Politics has nothing to do with the battlefield,” Hegseth said, as Democratic senators accuse him of politicizing the military. “This is about warfighting capability.”

While Hegseth served as an infantry officer in the National Guard, there is no evidence that he attempted to attend the Army’s Ranger School — one of the most common leadership and small-unit tactics courses for infantry soldiers. Prior to 2015, women were prohibited from attending that course, but dozens have graduated from it since.

As Democratic senators have been decrying Hegseth for his comments about women in combat roles, Republican senators have been entering various letters from female military officers supporting Hegseth into the record of the hearing.

Military branches still require women to pass strict fitness tests for the most physically challenging specialty jobs, like the Army Rangers or Green Berets.

A small number of women have been able to meet the physical requirements to join those ranks.

Not every woman in the service takes the specialized fitness tests for entering those training courses, just as not all men take them either.