The deputy labor secretary, Julie Su, is facing headwinds in her full Senate confirmation vote to become labor secretary after a narrow 11-to-10 vote in committee. Although the administration has been quiet on who they would put up if she flops, there are others in the mix.

Ms. Su was picked by President Biden to succeed the former labor secretary, Martin Walsh. She was the labor secretary for the state of California before being narrowly confirmed to the deputy secretary position in a 51-to-47 vote. It’s her record in California, where she pursued various liberal labor policies, that have made her a lightning rod among conservative and some moderate senators.

Although Ms. Su made it through her hearings in the Senate Heath, Education, Labor, and Pensions Committee, her nomination was immediately polarizing, even among Democrats.

Some Democrats are on the fence about her confirmation to the position, with Senators Manchin, Kelly, and Tester undecided on whether they will vote to confirm. Some not affiliated with a political party but who caucus with the Democrats, like Senators Sinema and King, are also undecided.

All of the fence-sitting Democrats are facing tough re-election races except for Mr. Kelly, though he does come from Arizona, a competitive state. Ms. Sinema and Mr. King are also facing re-election battles in 2024.

Before Ms. Su was nominated, there were other names floated for the position, which could crop up again if her confirmation runs aground in the Senate.

Some of those names include Representatives Andy Levin and Sean Patrick Maloney, as well as the Association of Flight Attendants-CWA president, Sara Nelson, and a former deputy labor secretary, Christopher Lu.

Mr. Nelson appeared to have the backing of Senator Sanders’s camp in the Senate, and as the chairman of the committee his say could have considerable sway.

Mr. Maloney, a former Democratic congressman who lost his seat in 2022, on the other hand, immediately faced opposition from within his own party, with a fellow New York Democrat, Representative Alexandria Occasio-Cortez, saying that she “could not think of a more divisive candidate for the job.”

Since then, Mr. Sanders has gone to bat for Ms. Su, citing her strong support for union organizing and employee protection measures, saying that she’s “made it clear she’s prepared to stand up for working families.”

If Ms. Su’s support among Democrats is tenuous, then her support among Republicans is nonexistent, in stark contrast to Mr. Walsh who enjoyed bipartisan support at his confirmation vote, winning confirmation 68 to 29.

One outspoken lawmaker was the relatively moderate Senator Romney, who characterized the idea of confirming Ms. Su as “laughable” during a hearing.

“Despite given clear warnings of potential fraud, Julie Su failed to act — more than $30 billion in fraudulent unemployment benefits were authorized under her watch,” Mr. Romney said. “Her track record of mismanagement and gross negligence makes her a laughable choice for secretary of labor.”

Mr. Romney added that “the idea of promoting a person who’s had that experience to a position of leadership for the entire department of labor makes no sense at all.”

Outside the halls of Congress, Ms. Su has faced opposition from business groups and other opponents.

Big business groups like the International Franchise Association have been lobbying against Ms. Su, with a spokesman, Michael Layman, comparing Ms. Su to her predecessor after the vote.

“Today’s party-line vote is another reminder that Julie Su is no Marty Walsh, who advanced in a bipartisan 18-4 vote only two years ago,” Mr. Layman said.

Businesses have funded other lobbying groups, like one called Stand Against Su, which claims to be “a coalition of small businesses, freelancers, tipped workers, and franchisees working together to oppose Julie Su.”

They are attempting to paint Ms. Su as a radical for seeking to “eliminate the tipped minimum wage” and to make companies “liable for the work conditions of their contractors.”

On the other side, organized labor groups like the American Federation of Labor and Congress of Industrial Organizations, the AFL-CIO, are lobbying on Ms. Su’s behalf.

“We’re going to defend Julie against these baseless corporate special interests attacks,” the AFL-CIO president, Liz Shuler, told reporters. “Every senator, especially those that haven’t yet said that they’ll vote yes, needs to be aware of how much this confirmation means to working people’s lives.”

While most Republicans who have talked about the nomination have expressed sympathy to corporations opposing Ms. Su’s bid, some Democrats have argued that a lack of support from business interests is irrelevant to her qualifications.

“It’s the Department of Labor, not the Department of Labor and Corporations,” Senator Casey said. “It’s there for the workers.”