Andrew Puzder, President Donald Trump's labor secretary nominee, withdrew from consideration Wednesday amid growing resistance from Senate Republicans centered primarily on Puzder's past employment of an undocumented housekeeper.

The collapse of Puzder's nomination threw the White House into further turmoil just two days after the resignation of Trump's national security adviser, Michael Flynn, amid revelations that Flynn had spoken repeatedly, and possibly illegally, with the Russian ambassador last year about lifting U.S. sanctions.

Puzder's fate amplified the deteriorating relationship between the White House and Capitol Hill, where bipartisan support grew Wednesday for expanded investigations into ties between Trump, his presidential campaign and Russian officials.

The White House, including Trump, offered no comment on Puzder's withdrawal nor any indication of whom the president would nominate in the restaurant executive's place. Puzder issued a statement saying he was "honored" to have been nominated. "While I won't be serving in the administration, I fully support the President and his highly qualified team," he said.

A top Trump campaign supporter, Puzder had attracted widespread criticism regarding his business record and personal background. He was set to testify Thursday at a confirmation hearing that had been delayed for weeks to allow for the completion of an ethics review of his vast personal wealth.

Critics have railed against Puzder's positions against minimum-wage increases and more generous overtime benefits. Some have also accused him of sexism, pointed to a rancorous divorce that involved later-recanted allegations of domestic abuse as well as racy TV ads run by his restaurant chains that featured scantily clad women eating hamburgers.

But it was Puzder's hiring of an undocumented worker for domestic work - as well as his support for more liberalized immigration policies - that pushed several Senate Republicans away, they said.

Puzder had told the Senate Committee on Health, Education, Labor and Pensions this month that he had been unaware of the housekeeper's immigration status when he hired her and that he paid federal and state back taxes after terminating her employment.

Similar revelations have forced Cabinet nominees to withdraw dating to at least Bill Clinton's presidency, but it was less clear this year, in the unpredictable, rule-breaking era of Trump, whether that norm would apply. In the end, the revelation was particularly troubling to lawmakers because of the job Puzder was seeking: running the Labor Department.

Sen. Tim Scott, R-S.C., a member of the Senate health committee, said Wednesday that revelations about Puzder's personal employment practices gave him "serious concerns" that he had conveyed to Senate leaders. Three other GOP senators on the committee, Susan Collins (Maine), Johnny Isakson (Ga.) and Lisa Murkowski (Alaska), had also publicly voiced doubts.

In the hours before Puzder withdrew, 12 Republican senators "at a minimum" were withholding support, according to a senior Republican who spoke on the condition of anonymity to avoid political retribution. The quick erosion of support compelled Majority Leader Mitch McConnell, R-Ky., to tell the White House on Wednesday that Puzder lacked the support needed to survive, according to two senior Senate aides who requested anonymity. Shortly after that, Puzder withdrew.

Jeff Curry / Getty Images Protesters walk to a Hardee's restaurant during a rally against Andrew Puzder's nomination for labor secretary near the Hardee's Headquarters on February 13, 2017 in St Louis, Missouri. The protesters feel that Mr. Puzder will not have the best interest of workers in mind due to his record of being a critic of raising the minimum wage as well as expansion of overtime pay, paid sick leave and the Affordable Care Act. Protesters walk to a Hardee's restaurant during a rally against Andrew Puzder's nomination for labor secretary near the Hardee's Headquarters on February 13, 2017 in St Louis, Missouri. The protesters feel that Mr. Puzder will not have the best interest of workers in mind due to his record of being a critic of raising the minimum wage as well as expansion of overtime pay, paid sick leave and the Affordable Care Act. (Jeff Curry / Getty Images) (Jeff Curry / Getty Images)

Senators may yet face another contentious confirmation vote Thursday, when Rep. Mick Mulvaney, R-S.C., Trump's nominee to lead the Office of Management and Budget, is scheduled for a final vote on the Senate floor. On Wednesday, Mulvaney lost the backing of Sen. John McCain, R-Ariz., who objects to Mulvaney's support for military spending cuts.

Puzder has spent much of his career in the restaurant industry speaking out against wage and labor regulations. The former commercial trial lawyer has been a staunch opponent of rules finalized by the Labor Department last year - and since put on hold - that would have expanded the number of people eligible for overtime pay. He also has been critical of substantially increasing the minimum wage, arguing that it could push companies to cut jobs and encourage businesses to invest more money in automation.

As a result, Puzder's nomination immediately came under intense scrutiny from unions, labor groups and consumer advocates who worried the executive would prioritize businesses over workers. As recently as this week, workers from his fast-food chain and advocates for a higher minimum wage marched outside of CKE's restaurants to protest the nomination. Worker advocates had also hand-delivered petitions to senators' local offices and organized trips for CKE employees to travel to Capitol Hill and share their grievances with senators.

Democrats cheered Puzder's withdrawal and sought to take credit for helping pressure Republicans to withdraw support.

Senate Minority Leader Charles Schumer, D-N.Y., called Puzder's decision "a victory for the American worker. Puzder should never have even been nominated to lead the Labor Department, and Senate Republicans clearly recognized this, too." He called on Trump to nominate someone who "champions workers' rights rather than suppresses them."

Progressives and Democrats said they hoped Trump's next pick for labor secretary would be someone with a clear willingness to speak up for disadvantaged workers.

"We need a labor secretary in the mainstream who supports the workplace protections that he or she would be charged with enforcing - and who cares about workers," said Emily Martin, general counsel for the National Women's Law Center, which opposed Puzder's nomination because of "sexist" advertising run by Carl's Jr. and Hardee's - two of Puzder's restaurant chains - and reports of harassment from employees working for the chain.

Several names that had emerged on Trump's shortlist for labor secretary late last year began recirculating Wednesday. Among them: Rep. Lou Barletta, R-Pa., and Wisconsin Gov. Scott Walker. After Puzder's withdrawal Wednesday, Walker tweeted: "The future is too bright in WI for me to do anything other than being Governor."

Puzder would have been the first labor secretary since the Reagan era to take the job without some experience in public service. He made a minor foray into politics in 2011, when he served as an economic adviser and spokesman for Republican presidential candidate Mitt Romney, who recently endorsed his nomination.

In 2016, Puzder was an avid Trump supporter. In addition to serving as an economic adviser to his campaign, he and his wife, Deanna Puzder, contributed a total of $332,000 to Trump's bid, joint fundraising committees and to the Republican National Committee, according to the Federal Election Commission.