Pete Hegseth, President-elect Donald J. Trump’s pick to lead the Pentagon, repeatedly denied allegations of misconduct against him on Tuesday and refused to say whether sexual assault, excessive drinking or marital infidelity should disqualify someone from being defense secretary .

Under questioning from Senator Tim Kaine, Democrat of Virginia, Mr. Hegseth dismissed what he said were “false allegations” about his behavior.

He testified before the Senate Armed Services Committee that he was a changed man, but at the same time denied all allegations of misconduct against him, saying it was a smear campaign orchestrated by left-leaning media and anonymous sources.

He also refused to say whether a person who committed the crimes he was accused of would be fit to lead the Pentagon.

“You can’t tell me whether someone who has committed a sexual assault will be disqualified from being defense secretary?” Mr. Kaine replied.

“Senator, I know that in my case – and I’m only speaking of my case – it was a false claim,” Mr. Hegseth responded.

Mr. Kaine then asked Mr. Hegseth if he had ever committed an act of physical violence against any of his three spouses. He denied this – but refused to say whether such behavior would be disqualifying.

Mr. Hegseth also refused to engage when Mr. Kaine asked whether someone who was publicly drunk, as some former colleagues have accused him, should be at the top of the Defense Department. The senator referred to allegations that a drunken Mr. Hegseth shouted “Kill all Muslims” at a work event at a bar and, on another occasion, took colleagues to a strip club where he tried to dance with strippers.

Mr. Kaine also rejected Mr. Hegseth’s efforts to dismiss the charges against him.

“Are you saying this was all anonymous? “We’ve seen records where all of these names included names, including your own mother’s name,” Mr Kaine said, adding: “So don’t make this an anonymous press matter.”

During his questioning, Mr. Kaine tried to argue that Mr. Hegseth’s past behavior made it clear that he should not do the job for which Mr. Trump had chosen him. Mr Kaine noted evidence of Mr Hegseth’s previous adultery and questioned whether he would treat the oath of office as defense secretary the same as his wedding vows.

Mr. Kaine also pointed out that Mr. Hegseth had fathered a child with the woman who later became his third wife while he was still married to his second wife, and that in 2017 there was an encounter with a woman who accused him of sexual assault – which Mr Hegseth has said was consensual – at least fraud, if not a crime.

Mr Hegseth responded by arguing he had been “falsely accused – fully, comprehensively investigated and fully exonerated”.

“Can you so casually cheat on a second wife and then cheat on the mother of a child two months before?” Mr Kaine replied. “How is this completely clear?”

Mr. Hegseth added that he had been redeemed by his “Lord and Savior” for his mistakes in life.

John Ismay And Eric Smith contributed to reporting.