WASHINGTON — Three Senate Democrats filed a lawsuit Monday arguing that Acting Attorney General Matthew Whitaker’s appointment is unconstitutional and asking a federal judge to remove him.

The suit was filed by Sens. Richard Blumenthal of Connecticut, Mazie Hirono of Hawaii and Sheldon Whitehouse of Rhode Island.

Whitaker was chief of staff to Attorney General Jeff Sessions and was elevated to the top job after Sessions was ousted by President Donald Trump on Nov. 7.

The Constitution’s Appointments Clause requires that the Senate confirm all principal officials before they can serve in their office.

The Justice Department released a legal opinion last week that said Whitaker’s appointment would not violate the clause because he is serving in an acting capacity. The opinion concluded that Whitaker, even without Senate confirmation, may serve in an acting capacity because he has been at the department for more than a year at a “sufficiently senior pay level.”