Montana Gov. Steve Bullock Steve BullockCourt removes Pendley from role as public lands chief On The Trail: Making sense of this week's polling tsunami McConnell locks down key GOP votes in Supreme Court fight MORE (D), a 2020 presidential candidate, said Wednesday that President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE's personal lawyer Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE should be "behind bars" over his dealings with Ukraine.

“As [state] attorney general, I saw criminals along the way and knew when they were engaged in criminal behavior. You look at what Rudy Giuliani has done, using the White House — basically the Oval Office — to have meetings about foreign nationals," Bullock said in a CNN interview.

“Here's a guy right now that should be behind bars,” the governor added.

ADVERTISEMENT

Bullock also said that Attorney General William Barr Bill BarrFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Why a backdoor to encrypted data is detrimental to cybersecurity and data integrity FBI official who worked with Mueller raised doubts about Russia investigation MORE should recuse himself from the matter because he was referenced in the rough transcript released by the White House of President Trump's July 25 call with Ukrainian President Volodymyr Zelensky. In the call, which is at the center of House Democrats' impeachment inquiry, Trump pressed for an investigation into former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and his son Hunter, telling Zelensky to coordinate with Giuliani and Barr.

"You look at Bill Barr, referenced five times in the transcript ... this guy should recuse himself," Bullock said.

Trump has denied any wrongdoing in his relations with Kiev and repeatedly rejected the idea that there was any quid pro quo, despite the fact that that the call came days after he delayed hundreds of millions of dollars in aid to Ukraine.

Multiple witnesses in the House's impeachment probe have said officials were uneasy with the foreign policy role played by Giuliani, who doesn't have an official title in the administration.

Bullock is among more than a dozen people running for the 2020 Democratic presidential nomination. Thus far, he has failed to make a significant impression in polling.