Ousted Social Security commissioner Andrew Saul, the Trump appointee who declared Friday he would defy his firing by President Biden, on Monday found his access to agency computers cut off, even as his acting replacement moved to undo his policies.

“I’m here to do the job,” Saul said from his home in Katonah, N.Y., where he had led the agency since the coronavirus pandemic forced most operations to shift in March 2020 to remote work, “but I can’t do anything with the communications shut down.”

Saul, 74, called his firing and that of his deputy David Black, in an email from the White House Personnel Office, a “palace coup” that he said blindsided him, given that his six-year term was not set to expire until 2025. As Republicans made plans to defend him, Saul said he had no public announcement — yet — on his strategy to remain in office as the “duly confirmed Social Security commissioner.”

“There will be more,” said Saul, a wealthy former women’s apparel executive and prominent Republican donor who had served on the board of a conservative think tank that has called for cuts to Social Security benefits. “Stay tuned.”

His acting successor, Biden appointee Kilolo Kijakazi, took the reins Monday and was briefed by her staff on the agency’s top priorities, advocates in touch with her office said, including much anticipated planning for the safe reopening of Social Security’s national network of 1,200 field offices. The agency has been under pressure for months from lawmakers in both parties to return to serving the public in person after complaints from constituents who do not have access to the Internet.

“Acting Commissioner Kijakazi is engaging with her leadership team across the agency as she transitions into her new job,” spokesman Mark Hinkle wrote in an email. Saul’s name and that of deputy commissioner David Black, who resigned Friday following a request from the White House, were stripped from the agency’s organization chart.

Experts in federal personnel law, meanwhile, said it was doubtful that Saul could successfully sue the administration to get his job back, following two rulings by the Supreme Court that affirmed the authority of the president to fire the head of an independent agency with a single leader.

“I think he can make a lot of noise and get the Republicans to make noise,” said Nancy Altman, an attorney and president of Social Security Works, an advocacy group that had called for Saul to go, “but in terms of the law, I would be shocked if a court found the president didn’t have the power to fire him.” At the most, Altman and others said, a court may find him eligible for financial compensation — but not return him to his job.

Saul’s firing was Biden’s latest dismissal of a Trump-appointed head of an independent agency whose terms have traditionally been fixed to insulate the agency from politics. Biden removed the head of the Federal Housing Finance Agency in late June after the Supreme Court ruled that he had the authority to do so. The court last year ruled that Trump was within his rights to similarly remove the director of the Consumer Financial Protection Bureau.

But the Social Security Administration is far more well known to Americans, and the political fallout from Saul’s ouster looked to have broader repercussions. The other difference: Saul’s refusal on Friday to resign, as Biden initially requested, and to fight his later firing. The Social Security Administration pays out more than $1 trillion a year in benefits to seniors, the disabled and low-income Americans.

As head of an independent agency whose leadership has historically straddled incoming and outgoing presidential administrations, Saul had served for six months under Biden. But he had alienated key Democratic constituencies with a get-tough approach to federal employee unions and policies designed to clamp down on Americans’ eligibility for benefits. Labor leaders, advocates for the disabled and lawmakers on Capitol Hill called for months on Biden to dismiss him, asserting that he was a right-wing Trump advocate whose agenda was at odds with the administration’s.

A White House spokesman said Monday that any questions about Saul’s service to the federal government were resolved last week.

“As you know, the President asked for Andrew Saul’s resignation on Friday, and after he refused to submit it, his employment was terminated,” said Chris Meagher, a deputy White House press secretary. “As with any employment termination, the government has taken steps to offboard Andrew Saul as we would any other former employee.”

But Senate Republicans said they do not plan to let Saul’s firing go quietly, and will seek to bring attention to what they called an ill-advised attempt by Biden to politicize a familiar, nonpartisan part of the federal government that touches 64 million Americans a year.

Compared with the consumer protection and housing agency firings, Biden’s dismissal of the Social Security leader stands as unprecedented and far more significant, they said.

Senate GOP aides, speaking on the condition of anonymity to discuss political strategy, said they plan floor speeches starting this week — possibly by Minority Leader Mitch McConnell (R-Ky.) and Charles E. Grassley (R-Iowa), a former Finance Committee chairman who has long taken an interest in the Social Security Administration — to express their dismay with the White House.

They also planned to focus on Saul’s 2019 confirmation, by a vote of 77 to 16, as a sign of rare bipartisanship.

Republicans also said they are considering procedural actions to block any permanent Biden nominees to the agency on the Senate floor.

“It’s not like Saul was a blazing partisan,” said one Senate GOP aide. “Our view is that longer terms for agencies like this exist for a reason.” Saul’s confirmation was not a small vote, and we plan to protect the Senate position in appointments.”

This is not the first time that confusion has reigned over the firing of a head of an independent agency. When the outgoing head of the Consumer Financial Protection Bureau named an acting director to lead the watchdog agency in 2017, Trump appointed his own head, then-White House budget director Mick Mulvaney.

The confusion over who was rightfully in charge set up a legal clash that eventually landed at the Supreme Court, as the high-ranking internal official sued to block Trump from installing Mulvaney. The agency was in turmoil for months as Mulvaney eventually took over.

As the partisan fallout from Saul’s firing continues, Kijakazi is confronting the demand for changes from his policies by the administration and advocates. At the top of the list is a restoration of harmony with the unions representing administrative law judges and the rest of the more than 60,000 employees at Social Security, who clashed with Saul over union rights, working conditions and how much low-income and disabled American receiving disability benefits should have to prove their eligibility.

While more and more routine business can be done online, the field office staff gives in-person assistance on complex matters, among them applications for disability programs that have plunged during the pandemic.

Biden also has laid out an expansive plan for the program, pledging during his campaign to expand Social Security benefits and remove some policies that advocates say make it harder for those in need to get benefits and continue to receive them.

“There’s a myth that Social Security can be above politics,” Altman said. “But it’s obvious that every decision you make is a policy decision.”