Senate Democrats filed a lawsuit Monday challenging President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE’s decision to name Matthew Whitaker acting attorney general.

The lawsuit brought by Sens. Richard Blumenthal (D-Conn.), Sheldon Whitehouse Sheldon WhitehouseFeinstein 'surprised and taken aback' by suggestion she's not up for Supreme Court fight Hillicon Valley: Murky TikTok deal raises questions about China's role | Twitter investigating automated image previews over apparent algorithmic bias | House approves bill making hacking federal voting systems a crime House approves legislation making hacking voting systems a federal crime MORE (D-R.I.) and Mazie Hirono Mazie Keiko HironoManchin defends Supreme Court candidate Barrett: 'It's awful to bring in religion' Democrats shoot down talk of expanding Supreme Court Democrats unveil plan declaring racism a public health issue MORE (D-Hawaii) in the U.S. District Court for the District of Columbia marks the latest challenge in what’s been a flurry of litigation fighting the interim appointment.

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The Democrats — all member of the Senate Judiciary Committee — argue in the 17-page complaint that Whitaker’s appointment violated the appointments clause of the constitution, which requires principal federal officers be appointed only with the Senate’s advice and consent.

Trump named Whitaker to the acting role earlier this month after former Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE submitted his resignation at the president’s request. Whitaker had been Sessions’s chief of staff, a role that does not require Senate confirmation.

“The U.S. Senate has not consented to Mr. Whitaker serving in any office within the federal government, let alone the highest office of the [Department of Justice],” the Democrats said.

“Indeed, before deciding whether to give their consent to Mr. Whitaker serving in such a role, Plaintiffs and other members of the Senate would have the opportunity to consider his espoused legal views, his affiliation with a company that is under criminal investigation for defrauding consumers, and his public comments criticizing and proposing to curtail ongoing DOJ investigations that implicate the President.”

Maryland was first to challenge the appointment in an existing lawsuit to protect provisions of the Affordable Care Act that cover people with pre-existing conditions.

On Wednesday, attorneys in an immigration case before the 2nd Circuit Court of Appeals asked the court to issue a temporary order that to block the government from moving forward in the case with Whitaker serving as acting attorney general.

And, late Friday, attorneys in a gun rights case pending before the Supreme Court asked the justices to issue an order that name Deputy Attorney General Rod Rosenstein to the position instead.

After Democrats said last week they were considering bringing the lawsuit forward, legal scholars questioned whether it would survive in court. Some law professors questioned if Democrats alone have the required injury to bring the lawsuit forward.

Stephen Vladeck, a law professor at the University of Texas School of Law, said then that the Senate as an institution has to be the one to assert they were injured by Trump’s decision to appoint Whitaker.

Others, meanwhile, argued government institutions can’t sue other government institutions.

In their lawsuit, Blumenthal, Hirono and Whitehouse argue Trump unlawfully denied them their right, as sitting U.S. senators, to vote on whether to consent to Whitaker’s appointment to that role.

“Unlawfully denying legislators their right to cast an effective vote robs them of one of their core powers and responsibilities,” they said.

Complete vote nullification, they said, is clearly a type of an institutional injury that's sufficient to give them standing to sue.

Updated at 11:22 a.m.