President Trump is coming under bipartisan scrutiny in Congress after he ousted two inspectors general and publicly criticized a third — actions that have left lawmakers wrestling yet again with an administration that has repeatedly flouted efforts at independent oversight since Trump took office.

His resistance to the watchdog system established after the ­Watergate scandal come on two fronts that have largely defined the Trump presidency: His impeachment, which was triggered by his attempts to pressure Ukraine into conducting a political investigation of one of his domestic rivals; and his administration’s management of the ongoing coronavirus pandemic, in which trillions of taxpayer dollars are being disbursed.

Trump’s dismissal of Michael Atkinson, the intelligence community’s inspector general, has in particular troubled influential Senate Republicans who are pushing the president for a more detailed explanation of why Atkinson was suddenly booted from his position late last week.

Atkinson was the official who notified Congress last September of an anonymous whistleblower complaint about Trump’s Ukraine dealings — a notification that set off a chain of events that led to the president’s impeachment by the House and eventual acquittal in a Senate trial.

Sen. Charles E. Grassley (R-Iowa), who for decades has championed congressional oversight, is drafting a letter to the president seeking that explanation about Atkinson. Grassley’s effort has been endorsed by Sens. Mitt Romney (R-Utah), Susan Collins (R-Maine) and Democrats in the chamber.

But lawmakers also are aware that they are, again, confronting a president who has repeatedly defied oversight by the legislative branch, raising questions about whether new safeguards established amid the pandemic will be effective against Trump. The president has shown little hesitation in dismissing independent watchdogs, ignoring congressional subpoenas and barring current and former administration officials from cooperating with investigations.

After firing Atkinson last week, Trump this week removed Glenn Fine, who had been the acting inspector general for the Pentagon and was to chair a federal panel overseeing the Trump administration’s management of the $2 trillion coronavirus rescue package passed by Congress last month.

The president also was critical of Christi A. Grimm, the principal deputy inspector general at the Department of Health and Human Services because her office released a report this week that found a “severe” and “widespread” shortage of testing supplies and protective gear at hospitals dealing with the pandemic.

Despite some pockets of concern among Republicans, GOP lawmakers have long been deferential to Trump’s presidential prerogative on matters of personnel and policy, reluctant to challenge a party leader with overwhelming support from the GOP base.

“Oversight is important, and we tend to do our part from the congressional side when it comes to implementation of all this,” Senate Majority Whip John Thune (S.D.), the No. 2 Senate Republican, said in an interview Wednesday. “But I guess what I would tell you is what we’ve always said: Whether we agree with some of those decisions or not, the president does get to make those picks and those choices.”

Many Democrats worry that oversight of the coronavirus stimulus will become the latest instance where the legislative and executive branches become bogged down in warfare over their respective powers, with the judiciary failing to resolve those disputes in a timely manner.

“We have discovered with this president how much our democratic system and separation of branches actually operates on respect of norms,” said Rep. Gerald E. Connolly (D-Va.), chairman of the House Oversight subcommittee on government operations. “This president has just blown through all of that and doesn’t care, so we’re going to have to think about statutory restraints on the president.”

In an interview with The Washington Post, House Speaker Nancy Pelosi (D-Calif.) said of Trump: “He dishonors the Constitution. He degrades the environment of what our country is.”

In one sense, Trump’s ouster of Atkinson as the intelligence community’s watchdog was months in the making.

White House officials said Trump was furious with the inspector general for his role in the Ukraine matter and wanted to fire him even late last year — amid the impeachment proceedings in Congress — but was talked out of it.

Johnny McEntee, the president’s new head of presidential personnel, has spoken to Trump in recent weeks about inspectors general as he reviews employees across the government whom he considers disloyal to the president, according to two White House officials who spoke on the condition of anonymity to disclose private deliberations.

In addition to McEntee, Trump has talked to new White House chief of staff Mark Meadows about what the president views as problems with the inspectors general in recent weeks, said a senior administration official, who, like the others, spoke on the condition of anonymity to comment freely.

In 2017, Trump and his senior advisers discussed replacing inspectors general with ones who were more politically aligned with the president and would be more likely to investigate previous Democratic administrations, according to a former senior administration official.

But they were concerned there would be significant pushback in Congress if they replaced inspectors general en masse.

Yet Trump has recently lamented to aides that the administration did not appoint more inspectors general earlier in Trump’s tenure, and an effort was made late last week to rush a flurry of appointments, one administration official said.

Late Friday evening, the White House announced a slate of five inspector general nominees, including Brian Miller, a senior associate White House counsel who has been tapped to oversee a $500 billion rescue fund for distressed industries created as part of the $2 trillion coronavirus stimulus law.

“My worry is he’s trying to make it as easy as possible to steer relief funds to his political allies and away from his political opponents,” Sen. Chris Murphy (D-Conn.) said of the president Wednesday. “It’s part of his campaign to undermine these IGs and make them appear political. These are all career government employees.”

During negotiations on the massive rescue bill, Trump told reporters, “I’ll be the oversight.” He further unnerved Democrats when he coupled signing the bill into law with a signing statement disputing the authority of the new inspector general to notify Congress if the executive branch was not providing information requested by the inspector general.

The president’s actions prompted Pelosi to announce last week the creation of a select committee with subpoena powers to scrutinize the administration’s response to the pandemic and its management of the rescue law.

On Atkinson, the letter from Grassley addressed to Trump has yet to be finalized and made public. But a draft version reviewed by The Washington Post notes that a president is required by law to inform the House and Senate Intelligence committees of his reasons for dismissing an intelligence community inspector general at least 30 days before that person is removed — which didn’t appear to happen with Atkinson.

The reason that Trump has given publicly — that he has lost confidence in Atkinson — is not satisfactory without additional explanation, the letter also says. The senators plan to tell Trump in the letter that “it is our responsibility to confirm that there are clear, substantial reasons for removal,” according to the draft.

“I think it’s a legitimate line of inquiry to ask some questions about that,” Thune said of the Atkinson letter led by Grassley. “It’s a fairly big move.”

The effort to seek answers about Atkinson’s ouster mirrors a letter drafted by Grassley in 2009 after then-President Barack Obama dismissed Gerald Walpin, the inspector general for the Corporation for National and Community Service, which oversees the AmeriCorps program. That move was criticized by Democratic and Republican senators at the time because the White House did not follow proper procedures in removing Walpin.

The Obama White House had said it had lost confidence in Walpin — essentially the same reason that Trump is giving for Atkinson’s removal.

The White House press office did not immediately respond to questions about the congressional objections to the administration’s treatment of the inspectors general — or about the proposed legislative response.

The new coronavirus law creates several layers of oversight of the administration’s pandemic management efforts.

In addition to the post to be held by Miller, it establishes the five-member commission that is to scrutinize the $500 billion fund, with each of the four congressional leaders choosing a member, with a fifth member to be selected jointly by Pelosi and Senate Majority Leader Mitch McConnell (R-Ky.). Senate Minority Leader Charles E. Schumer (D-N.Y.) is the only one of the four to have announced a selection — Bharat Ramamurti, a former top aide to Sen. Elizabeth Warren (D-Mass.).

Fine, a career official who had served under Republican and Democratic presidents, had been selected by the leader of a council of inspectors general to head the Pandemic Response Accountability Committee — which would conduct and coordinate audits, with investigators looking for waste, fraud and abuse of taxpayer money in the disbursement of loans, loan guarantees and financial payments to households and businesses.

Senior congressional officials believe it was premature to know whether Congress will establish more oversight provisions in future virus bills. But on Wednesday, a coalition of good-government groups pressed lawmakers to include legislative protection for inspectors general in the next package.

The reform groups are circulating proposed legislative language that would prohibit the removal of an inspector general except under a tightly limited list of circumstances. The proposal they are recommending is similar to one passed by the House in 2008 when Congress amended the Inspectors General Act. The House language was dropped from the bill in the Senate before final passage.

“I believe the bill they are working on for additional emergency funding must include protections for the IGs,” said Danielle Brian of the Project on Government Oversight, which is part of the lobbying coalition. “This is the only way we can assure that the people who need the emergency funding are going to get it.”

Connolly, in concert with Oversight Committee Chairman Carolyn B. Maloney (D-N.Y.) and Rep. Stephen F. Lynch (D-Mass.), introduced legislation Wednesday that would modify the oversight provisions of the coronavirus law to allow a broader range of inspectors general, including Fine, to participate. Sen. Richard Blumenthal (D-Conn.) is also drafting a bill that would bar the president from dismissing any inspectors general without “evidence-based good cause” — and allow anyone affected by the firing the right to stop it in court.

“If anything deserves careful oversight and accountability and auditing, it’s this,” Connolly said.