Washington (CNN) - Over 25 years ago, Joe Biden, then the chairman of the Senate Judiciary Committee, endorsed the confirmation of a "refreshing" and "honest" young William Barr for attorney general.
Tuesday, Barr, President Donald Trump's choice to take over the Justice Department, will be confronted by senators more dug in to their partisan camps and anxious about how he would oversee the special counsel probe that appears to be nearing a fiery finish.
Barr's nomination has taken on new urgency for Democrats in recent weeks as a clearer picture of his skepticism of Robert Mueller's investigation into whether the Trump team played any role in Russian election interference has emerged.
On Tuesday, Barr will promise to let Mueller complete his investigation without political interference, and will say that he wants to "provide as much transparency as I can" into any conclusions the special counsel makes, according to his prepared testimony.
But Democrats on the Senate panel, among them a host of possible 2020 presidential contenders including Sens. Cory Booker of New Jersey, Kamala Harris of California and Amy Klobuchar of Minnesota, are prepared to press Barr further, and have scrutinized his views on executive power and a memo he wrote last year criticizing a central element of Mueller's probe, a Democratic aide said.
Democratic staff have drafted dozens of questions around the investigation that some senators plan to ask Barr, with the goal of extracting a commitment that he will recuse himself from oversight of the probe, according to the aide.
"I want an ironclad commitment that he will protect the special counsel from political interference and recuse himself if he refuses to disavow the points that he made in his memorandum," Sen. Richard Blumenthal, a committee Democrat from Connecticut, said last week..
Proponent of presidential power
Before he claimed some of Washington's most influential legal perches, Barr studied law in night classes while he worked at the CIA.
In the agency's legislative counsel's office, Barr came in close contact at times with George H.W. Bush, then President Gerald Ford's CIA director, providing him with legal advice around questions from Congress.
Barr would continue his counsel to Bush, later becoming that administration's assistant attorney general in charge of the Justice Department's Office of Legal Counsel, where he helped shape legal opinions that influenced White House policy and action.
He was selected for the role, he has said, because of his views on strong executive authority, and in his 1989 confirmation hearing for the office, he made clear that he believed the Justice Department owed loyalty to the administration.
"He is the president's lawyer," Barr said of the attorney general. "He is the lawyer for the Cabinet."
Barr's deference lies in part with his beliefs on executive authority, which are in line with the unitary executive theory, a school of legal thought that draws a vision of uncompromising presidential power from the Constitution.
In the memo he sent last year to senior Justice Department officials, Barr reached the conclusion that Trump's interactions with ex-FBI Director James Comey would not constitute obstruction of justice because the president has "plenary power over law enforcement" and "complete authority to start or stop a law enforcement proceeding."
Writing for the legal website Just Security, Marty Lederman, a former Obama Office of Legal Counsel official and Georgetown University law professor, called the Mueller memo an example of "uber unitary executive" theory and said Barr's claims were "shockingly categorical" and "extreme."
Barr has since said he wrote the memo of his own accord and not at the request of the Trump administration. The President "has sought no assurances, promises, or commitments from me of any kind, either express or implied, and I have not given him any, other than that I would run the Department with professionalism and integrity," he will say in his testimony.
Despite his hard-line ideology, supporters of Barr point toward instances in his first Justice Department tenure that they say show he approached decisions based on an honest review of the facts, like when he told the White House there was no precedent to support the desire of some Republicans to use a line-item veto that would give the president a strategic advantage over lawmakers.
Barr, like many Democrats who would follow him, was also highly critical of the independent counsel statute that allowed specially designated prosecutors to investigate government misconduct. Nevertheless, he saw a number of outside prosecutors appointed during his tenure, and allowed others to proceed without interference.
Speaking at the University of Virginia's Miller Center of Public Affairs in 2001, Barr described how Bush had been "infuriated" by an indictment brought by an independent counsel only days before he hoped to be reelected.
"He landed in the yard in the helicopter. And he waved me into his office, and I went in. He asked me about the indictment that had come down the Friday before the last election," Barr said of Bush. "He did say to me that he felt that that indictment had cost him the election. He was very infuriated by it."
Democrats also see parallels between Barr's support of the pardons that capped the Iran-Contra scandal and potential moves by Trump in the waning days of the Mueller probe, and will seek more testimony on his views, the aide said.
Bush granted the pardons to six former government officials in the arms sales scandal days before the trial of former Defense Secretary Caspar Weinberger, which threatened to reveal new evidence of lies that members of the Reagan administration had told Congress about the deal.
Lawrence Walsh, the independent counsel who oversaw the inquiry, said at the time that the pardon "undermines the principle that no man is above the law."
"It demonstrates that powerful people with powerful allies can commit serious crimes in high office -- deliberately abusing the public trust without consequence," Walsh said.
Barr, then Bush's attorney general with oversight of the pardon office, told interviewers at the Miller Center in 2001 that he fully supported the move.
"I favored the broadest pardon authority," Barr said. "There were some people just arguing just for Weinberger. I said, 'No -- in for a penny, in for a pound.'"
Tuesday's hearing will be Barr's fourth time appearing before the Senate Judiciary Committee as he's sought postings at the Justice Department.
Senators are preparing to question Barr -- who's coming after a long absence from government service -- on his work during the time since as a corporate lawyer for major telecommunications companies, including on surveillance issues.
Democrats have also pored over thousands of pages of comments Barr has made as they try to understand his views on domestic policy issues, and will quiz him on how they may have changed since his last time in government, the committee aide said.
As attorney general in a time when the Justice Department had jurisdiction over most elements of immigration enforcement, Barr discussed the value of a fence along parts of the US-Mexico border to block illegal immigration, and increased the number of Border Patrol agents.
In a 1992 PBS interview, however, Barr called an extended border barrier "overkill."
"I think that's overkill, to put a barrier from one side of the border to the other," Barr said. "Illegal immigrants do not cross in the middle of the desert and walk hundreds of miles to the nearest city, they generally try to go up through certain specific routes."
The attorney general oversees the US immigration courts. As the partial government shutdown continues, more than 40,000 immigration hearings have been canceled or postponed due to courts being closed.
On abortion, Barr has stated his personal opposition, and in a 1992 interview on CNN he predicted that Roe v. Wade would be overturned.
"I think that Roe v. Wade will ultimately be overturned," Barr said on CNN's "Evans & Novak." "I think it'll fall of its own weight. It does not have any constitutional underpinnings."
Barr's views on torture will likely also be tested by Democrats following comments he made at a civil liberties and national security panel as a private citizen in 2005.
"Under the laws of war, absent a treaty, there is nothing wrong with coercive interrogation, applying pain, discomfort and other things to make people talk, so long as it doesn't cross the line and involve the gratuitous barbarity involved in torture," Barr said.
CORRECTION: This story has been updated to reflect that George H.W. Bush served as CIA director under then-President Gerald Ford.