Top House Democrats on Tuesday savaged the Trump administration’s plan to blow up the Office of Personnel Management, calling the effort to close the major federal agency a backdoor power play to weaken the federal workforce.

The hostile reception, alongside tepid support from Republicans, left the plan’s chances in doubt and raised the possibility that the administration would dismantle some of the agency’s functions on its own, even if Congress fails to pass legislation to do it.

“Today is a reckoning,” said Rep. Gerald E. Connolly (D-Va.), chairman of the House Oversight and Reform Committee’s panel on government operations, which held a three-hour hearing titled “The Administration’s War on a Merit Based Civil Service.”

“There is no clear and convincing reason for dismantling this key federal agency,” Connolly said, calling the plan a “a reckless endgame in search of a rationale” that was rushed through and would be unlikely to be approved by Congress.

Rep. Elijah E. Cummings (D-Md.), chairman of the full Oversight Committee, made a brief appearance at the start of the hearing to question whether the administration had made its case adequately.

The proposed breakup, which has consumed the personnel agency for more than a year, would pull apart OPM and its 5,565 federal employees and divide it among three other departments.

Most of its functions would move into the General Services Administration, the government’s real estate and procurement arm. OPM’s massive, backlogged security clearance system already is in the process of shifting to the Defense Department, through legislation previously passed by Congress.

OPM’s leadership would shift from an agency director to a Senate-confirmed deputy in GSA and a position within the White House budget office responsible for federal workforce policy that the president would appoint directly — but that would not require Senate confirmation.

Critics say the proposal is a ploy to politicize the civil service by installing political appointees close to the White House.

Trump officials formally proposed the shift last week, sending proposed legislation to Congress that would transfer most of the agency’s functions to the GSA and shift its leadership. No employees would be fired, and most would stay at their desks, since right now the GSA could not physically accommodate them. The administration estimates that zeroing out the agency would save $23 million a year through employee attrition and consolidation of contracts and services.

As she made the administration’s case on Tuesday, Margaret Weichert, deputy director for management at the Office of Management and Budget and acting OPM director, described the agency as ineffective and crippled by aging computer systems that resulted in a massive breach of employee data in 2015.

Weichert said the staff is so bogged down by technology problems that it cannot carry out its core mission of enacting policies to improve the 2.1 million-strong civil service — particularly by raising morale — and conduct succession planning for an aging workforce.

And she cited financial distress as a primary reason to kill the agency: The transfer of background investigations to the Pentagon is leaving a $70 million hole in its budget, money that was paid by other federal offices to vet employees for security clearances.

“This entity is not only failing in technology — it’s failing in its core mission,” Weichert said. “Administration after administration has tried to address these challenges.”

Other government officials, including the agency’s inspector general and a top federal auditor, took issue with the plan as poorly thought out and communicated to stakeholders.

Norbert Vint, OPM’s acting inspector general, said his office had been provided with no analysis of why the agency should break apart and no menu of alternatives showing how the administration reached its decision.

A Republican who led the OPM in the George W. Bush administration and served on the Trump transition team testified against the breakup, saying that federal personnel policy was designed to keep the civil service apolitical.

GOP lawmakers appeared unenthusiastic as well. Few spoke, and those who did were unhappy that the administration had waited until just hours before the hearing to provide details of the plan.

“I don’t think we’ve ever done a reorganization like this in the federal government,” said the subcommittee’s top Republican, Rep. Mark Meadows (R-N.C.), who seemed to press instead for a “more effective and efficient” personnel agency without dismantling it.

Rep. Glenn Grothman (R-Wis.) questioned whether such a major change could be carried out this year, as the administration had originally planned.

But the most pointed criticism was left to Democrats, who, while acknowledging the problems with OPM’s legacy computer systems, questioned the administration’s motives in breaking up a department with a government-wide role. “It just sounds like you’re proceeding on a wing and prayer here,” Rep. John Sarbanes (D-Md.) told Weichert, calling her justification “quite facile and a kind of double talk.”

Rep. Don Beyer (D-Va.), a lawmaker with tens of thousands of federal employees in his district, asked, “Why would we take an organization that’s apparently struggling and move it to a larger bureaucracy that will inevitably be less flexible?’’

The administration is asking Congress for $50 million in fiscal 2020 to carry out the reshuffling, which would be the first elimination of a major agency since the World War II era. Some former agencies, such as the Home Owners’ Loan Corp., which was prominent in the 1930s, once were large but shrank substantially before being eliminated.

Eliminating OPM could serve as a blueprint for closing other departments as the Trump administration moves to carry out the president’s campaign pledge to shrink government.

The OPM, created in 1978 to oversee the civil service, has a broad reach. It coordinates hiring, recruiting and performance policies across the government, oversees health insurance and benefits for millions of retirees and ensures that federal agencies protect employee rights under an apolitical merit system.

The move has also received a poor reception among Washington-area Senate Democrats, who have hundreds of thousands of federal employees in their districts. Late Monday, they wrote a letter to Russell Vought, the acting OMB director, accusing him of drafting the plan without consulting Congress, federal employee unions or groups representing managers and pressing him to explain how the White House could guarantee that federal employees would “continue to be insulated from the political impulses of this President and any future President.”

The plan has raised suspicions from federal employees, who have watched the administration attempt to freeze their pay, weaken the power of their unions and move to clear a faster path to discipline and firing.

J. David Cox, president of the American Federation of Government Employees, the largest federal employee union, assailed the plan as another assault on the civil service. “This administration has been trying to undermine the civil service since Day One, questioning the loyalty of federal employees,” he testified. “If the administration gets its way, GSA would provide fleets of leased employees, hired for discreet teams and available to be used, abused, discarded and replaced.”