Five months after President Joe Biden announced he was nominating Julie Su for labor secretary, congressional Republicans are ratcheting up their efforts to end her bid.

Su’s nomination cleared the Democratic-led Senate Health, Education, Labor and Pensions Committee in late April but has yet to come to a confirmation vote before the full Senate.

Earlier this month, a White House official urged two senators who caucus with Democrats — Joe Manchin, D-W.V., and Kyrsten Sinema, I-Ariz. — to reconsider their positions on Su, signaling she likely lacks the necessary votes to be confirmed. Manchin has publicly declared his opposition, but Sinema has not.

Previously the deputy labor secretary, Su has been serving as acting secretary since Marty Walsh left in March to lead the National Hockey League Players’ Association.

According to Republicans, no Cabinet nominee has ever served longer in an acting role when their party controlled both the Senate and White House.

Republicans oppose Su’s nomination, arguing, among other grievances, that when she was California’s labor secretary, fraudsters bilked the state out of $32 billion in unemployment claims and that, as U.S. deputy labor secretary, she helped impose vaccine mandates on businesses.

GOP lawmakers also blame Su for costing independent contractors work opportunities by pushing a law that reclassified them as employees.

The White House said Friday that Biden still supports Su and it is continuing to fight for her nomination, calling her highly qualified, experienced and proven. 

According to multiple reports, the White House is prepared to have Su serve as acting secretary indefinitely. An official told Axios earlier this month that such a tenure would be legal under a law that allows a deputy secretary to perform the duties of the secretary until a successor is appointed.

On Thursday, Republican Reps. Kevin Kiley of California and Virginia Foxx of North Carolina introduced a bill that aims to ensure Su’s acting role is temporary by instead enforcing the Federal Vacancies Reform Act, which limits an acting officer to 210 days. 

“Having made the worst possible pick for Labor Secretary, which the Senate is rightly rejecting, the President is trying to install his nominee anyways,” Kiley said in a statement. “ … Our legislation will prevent Su from indefinitely serving in defiance of Congress and taking her record of failure in California nationwide.”

“Su’s pathway to confirmation has stalled,” Foxx added. “For the sake of job creators and working Americans, Biden must pull Su. Instead, he has stretched the law to bypass a Senate confirmation process. Par for the course for a president accustomed to flouting the law to get his way.”

On Friday, a group of 20 Senate Republicans sent a letter to Biden also accusing him of circumventing the confirmation process and urging him to withdraw Su’s nomination.

“It is clear that Ms. Su does not have the necessary support to be confirmed, and we urge you to immediately withdraw her nomination,” the letter said.

“It is absolutely unacceptable for your administration to do an end-run around the constitutional obligation to see the advice and consent of the Senate — particularly for a nominee that has already demonstrated an inability to garner the necessary votes for confirmation,” the senators continued.

In addition, business groups — including the app-based trade association Flex and the Job Creators Network Foundation — are preparing to mount constitutional challenges if Su is not confirmed, Bloomberg Law reported.

“Simply put, by declining to act on Ms. Su’s nomination, the Senate is advising against the policies she has espoused and declining to consent to her leadership,” Flex CEO Kristin Sharp wrote Monday in a letter to Biden. 

At her confirmation hearing in April, Su, who would become the first Asian American to serve in Biden’s Cabinet as a secretary, defended her record. For instance, she said when she became aware of unemployment fraud in California, she quickly put an end to it and made changes to prevent further abuse. She said the reclassification law was needed because employers were avoiding paying their employees minimum wage, overtime and unemployment benefits by declaring them contractors. 

The Labor Department did not respond to a request for comment Friday on the House bill and senators’ letter.

A representative for Senate Majority Leader Chuck Schumer, D-N.Y., did not reply to an email asking about the status of a floor vote on Su’s nomination.