“The stakes are too high to allow the president to install an unconfirmed lackey to lead the Department of Justice — a lackey whose stated purpose, apparently, is undermining a major investigation into the president,” said Whitehouse in a statement. Whitaker served as U.S. Attorney for Iowa from 2004 to 2009, and sat on the board of a Miami-based scam company that hawked patents for everything from time travel technology to hot tubs.

The three senators filed suit with the aid of two nonprofit law firms — Protect Democracy and the Constitutional Accountability Center — joining a growing chorus of lawyers and politicians objecting to the appointment.

Whitaker, a Trump loyalist and vocal skeptic of special counsel Robert Mueller’s investigation into the president’s communications with Russia during the 2016 election, previously worked as former attorney General Jeff Sessions’ chief of staff. His appointment following Sessions’ ouster the day after the midterms circumvented the existing Justice Department hierarchy where Rod Rosenstein would have been next in line, blindsiding lawmakers and stoking fears that Trump’s ultimate goal was to dismantle the Mueller probe, which Whitaker now oversees.

Last week, a host of lawyers, including conservative Republicans from the Federalist Society, released statements against Whitaker’s appointment, and lawyers in Maryland asked the U.S. Supreme Court to intervene.

Under the Vacancies Reform Act, the president can appoint someone to a position that would normally require Senate confirmation, while he or she finds a permanent replacement. By law, Whitaker can serve for up to 210 days as Acting Attorney General – and potentially longer, depending on the confirmation process of his successor. And though his tenure at the helm of the Justice Department will be short-lived, Democrats fear that Whitaker could do significant damage.

And Senators say that another law, the Constitution Appointments Clause, makes it clear that the Senate is required to confirm high-ranking federal government officials including Attorney General, before they start work.

“President Trump is denying Senators our constitutional obligation and opportunity to do our job: scrutinizing the nomination of our nation’s top law enforcement official,” said Blumenthal in a statement. “The reason is simple: Whitaker would never pass the advice and consent test. In selecting a so-called “constitutional nobody” and thwarting every Senator’s constitutional duty, Trump leaves us no choice but to seek recourse through the courts.”