Attorney general nominee William Barr may have to recuse himself from special counsel Robert Mueller's Russia investigation, activists and attorneys say, pointing to at least two arguments that he cannot impartially supervise Mueller.

The arguments indicate pressure for recusal may come from both sides of the aisle: Democrats are concerned that Barr prejudged the Mueller investigation in a 20-page memo written in June; the other argument, emerging this week, is spurring fears among conservatives that he's personally too close to Mueller.

The friendship between Barr and Mueller wasn't widely discussed before Wednesday, when Sen. Lindsey Graham, R-S.C., told reporters that he spoke with Barr and was surprised to learn that Mueller attended Barr’s daughters’ weddings and that their wives attend the same Bible study.

The Barr memo, sent to the Justice Department, called any investigation of Trump on obstruction of justice charges as "fatally misconceived" and said that “Mueller should not be permitted to demand that the President submit to interrogation about alleged obstruction.”

University of Texas law professor John Dzienkowski, a legal ethics expert, said, “I think recusal based upon the memo is a stronger case than upon the existence of a friendship with Mueller."

Dzienkowski said the memo, which has not been released, would be grounds for recusal if it describes more than mere policy positions.

“If it goes into specifics of collusion or obstruction of justice, it could be viewed as prejudging the case without knowing the details, and that could be the basis for a recusal,” he said.

The personal relationship between Mueller and Barr, meanwhile, requires more subjective judgment.

“Barr could argue that the department has very clear guidelines as to how he is to consider this report and his friendship with Mueller would have no effect upon this supervisory role,” Dzienkowski said. “Of course, the closeness of the relationship may affect this decision. Pure casual friendship may be viewed differently from if Mueller or his wife were for example godparents of the Barr children.”

Other experts say friendships between boss and subordinate are not disqualifying by law or regulation.

Although attorneys general have recused themselves from cases out of mere abundance of caution, Fordham University law professor Bruce Green said. That’s because they had potential links to the subjects of investigations.

“The prosecutor's oversight of a subordinate is not like a judge's relationship with a lawyer or party, where you need a high degree of detachment, neutrality, and objectivity,” Green said.

“This is a one-industry town. If you recused everyone for church groups and wedding invitations, we would have to outsource most of government to foreign contractors,” said George Washington University law professor Jonathan Turley.

Still, some recusals are cloaked in mystery, guided by apparent personal links. After accepting a guilty plea from former national security adviser Michael Flynn, U.S. District Judge Rudolph Contreras, without explanation, recused himself. It later emerged that Contreras had social links to Peter Strzok, an FBI agent who had sent anti-Trump messages while working for Mueller.

Some conservative activists say Barr's recusal due to the friendship could be justified.

“The Establishment will ask General Barr if he is strong enough to stand up to President Trump. The real question should be, 'Is General Barr strong enough to stand up for President Trump,'” said Tom Fitton, president of the conservative transparency group Judicial Watch.

“I don’t think that recusal would be legally required, but it may happen for political reasons,” Fitton said.

Conservative legal activist Larry Klayman, who is suing Mueller on behalf of author Jerome Corsi, said “it does create the appearance of partiality and he's obviously going to be deferential to Mueller.”

Klayman said “everyone knows everyone in this town” and that by picking Barr, a longtime Washington attorney who served as attorney general in the 1990s, Trump “just got himself back in the same swamp he thought he had extricated himself from.

“The president should withdraw Bill Barr. There are other people he can get in there who are not cozy with Mueller,” Klayman said.

Paul Kamenar, an attorney challenging the constitutionality of Mueller’s investigation on behalf of former Roger Stone associate Andrew Miller, said he’s known Barr for years and trusts his judgment, though he expects Democrats to grill Barr on his memo during confirmation hearings next week.

Kamenar notes Barr “can voluntarily recuse himself from this or he can delegate his powers to [Deputy Attorney General Rod] Rosenstein or somebody else ... under the statute the AG can delegate his powers to any other office in the DOJ, [like Solicitor General] Noel Francisco or the assistant attorney general in charge of Criminal Division, so it's not just a recusal that defaults to Rosenstein, he can pick the person.”

Questions about Barr follow clashes over the suitability of Mueller, a former Trump golf club member, to lead the investigation, and over the appropriateness of Rosenstein supervising Mueller following former Attorney General Jeff Sessions’ recusal over undisclosed meetings with Russia’s ambassador. Rosenstein was a key player in events under review by Mueller, including the firing of FBI Director James Comey, whose ouster ostensibly was premised on a memo Rosenstein wrote.

Acting Attorney General Matthew Whitaker, who criticized Mueller before taking office and previously worked with former Trump campaign co-chair Sam Clovis, brushed aside questions about his own objectively. Last month, the Justice Department told Congress that ethics advisers believed Whitaker "should recuse himself ... because it was their view that a reasonable person with knowledge of the relevant facts likely would question [his] impartiality." Whitaker declined to step aside.

A Justice Department spokesperson directed the Washington Examiner to a previously released statement that "Mr. Barr’s memo would present no conflict as to his duties as Attorney General," but did not directly comment on whether recusal from the Mueller investigation is possible.