WASHINGTON ― President Donald Trump is “very close” to selecting an interim candidate to replace former FBI Director James Comey, he told White House reporters on Thursday.

Trump confirmed that former Sen. Joe Lieberman is his top choice, according to White House pool reports. The founder of Lieberman’s law firm ― Kasowitz, Benson, Torres & Friedman ― is one of the president’s top lawyers.

Per pooler @HallieJackson,Trump confirms Lieberman is his TOP PICK for FBI director, says he's "very close" to making a final choice. — Steven Portnoy (@stevenportnoy) May 18, 2017

Trump met on Wednesday with Lieberman and three other candidates: current acting FBI Director Andrew McCabe; Frank Keating, the former governor of Oklahoma who previously served as an FBI agent and in high-level positions in the Justice Department; and Richard McFeely, who served in the FBI for 24 years before retiring as executive assistant director in 2014.

OLIVIER DOULIERY via Getty Images Former Sen. Joe Lieberman leaves the West Wing of the White House after meeting with President Donald Trump on Wednesday.

Lieberman, who was the 2000 Democratic vice presidential nominee before losing a primary bid for re-election and becoming an independent, would be an unconventional choice. He has no federal law enforcement experience and, while currently at a high-profile law firm, is most associated as a centrist Democrat.

He has previously said that he would support an independent commission to investigate ties between Trump’s administration and Russia. But it is his background in politics that had Democrats reacting with severe reservation.

Sen. Claire McCaskill (D-Mo.) called it a “mistake” to select an elected official to the post, saying that the FBI director should be a law enforcement official. While Sen. Brian Schatz (D-Hawaii), in an interview with Huffpost, called the possible nomination “shocking.”

“There is no reason to appoint a politician to run the FBI,” Schatz said. “It is contrary to everything the FBI is about and it undermines the confidence that the public needs to have in the independence of the agency. And more to the point, it is not as if there is no one else qualified to do this job. There are literally dozens of people who would get a unanimous vote.”

It is rare for an FBI director to be appointed without the full backing of the Senate, Schatz noted. And he speculated that a Lieberman nomination would split the chamber.

A top Senate Democratic aide, likewise, put the prospects of immense opposition to the pick bluntly in an email to HuffPost: “There couldn’t possibly be worse time to take the unprecedented step of handing the FBI over to a politician. That absolutely includes Senator Lieberman.”

During a Thursday Democratic caucus lunch, Sens. Dick Durbin (Ill.) and Sheldon Whitehouse (R.I.) trashed the idea of Lieberman, or any politician, being in charge of the FBI, according to a senior Democratic aide who was in the private meeting. A majority of Democrats in the room said they agreed that he’s a terrible choice. Not a one defended Lieberman.

“The FBI director should be drawn from the ranks of career law enforcement‎, prosecutors or the FBI itself ― not politicians,” Durbin told HuffPost later.

Republicans, by contrast, praised Lieberman. Sen. Marco Rubio (R-Fla.) expressed “great admiration” for the former senator, Sen. John Cornyn (R-Texas) speculated that Lieberman could get 100 confirmation votes, and Sen. John McCain (R-Ariz.), said he would be “overjoyed” if Lieberman, who is a friend of his, were picked.

“Joe Lieberman has more experience than all of my Democrat colleagues combined, so screw them,” McCain said of Democrats’ concerns.

The need for a new FBI director came after Trump fired Comey last week, a stunning move that occurred amid the FBI’s ongoing investigation into the Trump campaign’s ties to Russia. A series of explosive reports over the last week have heightened the appearance that Trump interfered with the investigation. In particular, The New York Times reported that Trump asked Comey to shut down a separate probe into former national security adviser Michael Flynn’s contacts with Russian officials, according to a memo Comey wrote to document a meeting with Trump.

Jennifer Bendery contributed to this report.