WASHINGTON — The Senate advanced the nomination of Pete Hegseth as President Donald Trump's defense secretary Thursday on a largely party-line vote, despite grave objections from Democrats and stirring unease among Republicans over his behavior and qualifications to lead the U.S. military.

Two Republicans, Sen. Lisa Murkowski of Alaska and Sen. Susan Collins of Maine, broke ranks with Trump and his allies who have mounted an extensive public campaign to push Hegseth toward confirmation. The former combat veteran and Fox News host faces allegations of excessive drinking and aggressive actions toward women, which he has denied. The vote was 51-49, with a final vote on confirmation expected Friday.

Senate Democratic Leader Chuck Schumer implored his colleagues to think seriously, "Is this the best man we have to lead the greatest military in the world?"

Murkowksi, in a lengthy statement, said that his behaviors "starkly contrast" with what is expected of the military. She also noted his past statements that women should not fill military combat roles. Hegseth sought to temper those statements during the confirmation process.

"I remain concerned about the message that confirming Mr. Hegseth sends to women currently serving and those aspiring to join," Murkowski wrote on social media.

Murkowski said behavior that Hegseth has acknowledged, "including infidelity on multiple occasions," shows a lack of judgment. "These behaviors starkly contrast the values and discipline expected of service members," she said.

Collins said that while she appreciates Hegseth's "courageous military service and his ongoing commitment to our service members and their families, I am concerned that he does not have the experience and perspective necessary to succeed in the job."

She also said that after a lengthy discussion with Hegseth, "I am not convinced that his position on women serving in combat roles has changed."

Rarely has a Cabinet choice encountered such swirling allegations of wrongdoing. Trump is standing by Hegseth, and the chairman of the Senate Armed Services Committee has dismissed the claims as factually inaccurate.

It will take a simple majority of senators to confirm Hegseth's nomination. Most Republicans, who hold a 53-seat majority in the chamber, have signaled they will back the nominee, though Vice President JD Vance could be called in to break a tie vote.

"I am ironclad in my assessment that the nominee, Mr. Hegseth, is prepared to be the next secretary of defense," the chairman, Sen. Roger Wicker, R-Miss., said in a statement on the eve of voting. "The Senate needs to confirm this nominee as fast as possible."

A new president's national security nominees are often the first to be lined up for confirmation, to ensure U.S. safety at home and abroad. Already the Senate has overwhelmingly confirmed Marco Rubio as secretary of state in a unanimous vote, and confirmed John Ratcliffe as CIA director Thursday.

But Hegseth stands in a category of his own amid allegations that he sexually assaulted a woman at a Republican conference in California, which he has denied as a consensual encounter, and of heavy drinking at events when he led a veterans organization.

A new claim emerged this week in an affidavit from a former sister-in-law who claimed Hegseth was abusive to his second wife to the point that she feared for her safety. Hegseth has denied the allegation. In divorce proceedings, neither Hegseth nor the woman claimed to be a victim of domestic abuse.

Schumer said Thursday that Hegseth is unqualified for the job.

"One of the kindest words that might be used to describe Mr. Hegseth is erratic, and that's a term you don't want at DOD," Schumer said. "He has a clear problem of judgment."

A Princeton and Harvard-educated former combat veteran, Hegseth went on to make a career at Fox News, where he hosted a weekend show. Trump tapped him as the defense secretary to lead an organization with nearly 2.1 million service members, about 780,000 civilians and a budget of $850 billion.

During a fiery confirmation hearing, Hegseth swatted away allegations of wrongdoing one by one — dismissing them as "smears" — as he displayed his military credentials and vowed to bring "warrior culture" to the top Pentagon post.

Hegseth has promised not to drink on the job if confirmed.

Wicker said he had been briefed a third time on the FBI background investigation into Hegseth. He said "the allegations unfairly impugning his character do not pass scrutiny."

But senators have remained doubtful of his experience and abilities and the alleged behavior that could lead to reprimand or firing for military personnel he would now be expected to lead.

Still, Sen. Joni Ernst, R-Iowa, herself a combat veteran and sexual assault survivor, has signaled her backing.