Brett Kavanaugh, who has blamed “left-wing opposition groups” and people seeking “revenge on behalf of the Clintons” in defending himself against accusations of sexual assault, may be confirmed as early as this weekend as a justice on a Supreme Court that considers cases of sexual assault and partisan politics.

Kavanaugh, a forceful advocate of presidential immunity from subpoena or prosecution, would join a court that also often considers the scope of presidential powers, and may soon face disputes arising from the investigation of President Trump.

If Kavanaugh is confirmed, interested parties are virtually certain to ask him to recuse, or disqualify himself, from cases involving any of those issues. The law requires federal judges at all levels to recuse when they have conflicts of interest, but there is no way to enforce it against Supreme Court justices short of congressional impeachment.

Republican leaders have scheduled a vote on Friday to bring Kavanaugh’s nomination to the Senate floor, and could hold a confirmation vote as soon as Saturday. With Republicans holding a 51-49 Senate majority, the outcome depends on the reactions of two or three Republican senators to the FBI’s brief investigation into accusations of drunken sexual assaults by Kavanaugh as a high school and college student. He would succeed the retired Justice Anthony Kennedy on a court whose current members are ideologically divided 4-4.

The law requires federal judges to recuse themselves from any case in which their “impartiality might reasonably be questioned.” Questions about Kavanaugh’s impartiality proliferated last week after his blistering testimony before the Senate Judiciary Committee, which had just heard Christine Blasey Ford, a Palo Alto psychology professor, accuse him of trying to rape her as a teenager in 1982.

“This whole two-week effort has been a calculated and orchestrated political hit fueled with apparent pent-up anger about President Trump and the 2016 election, fear that has been unfairly stoked about my judicial record, revenge on behalf of the Clintons and millions of dollars in money from outside left-wing opposition groups,” Kavanaugh said. He was referring, in part, to his role as an assistant to Kenneth Starr in the investigation that led to the impeachment of President Bill Clinton.

But unlike lower-court judges, whose decisions can be appealed and whose ethics are subject to review by regional and national judicial bodies, a Supreme Court justice’s decision on recusal is not subject to review by the other justices, or by anyone else except the court of public opinion.

On the eve of Friday’s vote, Kavanaugh tried to fend off concerns that he is not suited for the job. He wrote in a column in the Wall Street Journal that he “might have been too emotional at times” in his testimony. If confirmed, he said, he would “keep an open mind in every case.”

Supreme Court justices “have a tremendous amount of autonomy and lack of review,” said James Sample, a Hofstra University law professor and expert on judicial recusals. While the anticipated requests for Kavanaugh to bow out of specific cases would be “a problem he himself created” with his Judiciary Committee testimony, Sample said, he would have reasons for refusing, including some recent examples from the high court.

Possibly the best-known case was in 2004, when Justice Antonin Scalia went on a duck-hunting trip with Vice President Dick Cheney and, a few months later, took part in a ruling on whether Cheney could withhold documents about an energy task force he had headed. Scalia voted in Cheney’s favor.

Scalia issued a memo defending his participation in the case, saying he had never discussed it with Cheney, that friendship was not grounds for recusal, and that “if a Supreme Court Justice can be bought so cheap, the Nation is in deeper trouble than I had imagined.”

More recently, some Republicans called for Justice Ruth Bader Ginsburg to recuse herself from a case over the legality of President Trump’s ban on travel to the United States from a number of countries, most of them predominantly Muslim. Their concern was based in media interviews during the 2016 presidential campaign in which Ginsburg had called Trump a “faker” who “says whatever comes into his head at the moment.” Trump responded by calling for Ginsburg to resign from the court.

Ginsburg apologized for her comments shortly afterward, calling them “ill-advised,” but did not offer an explanation for her later decision to take part in the travel ban case. This June, she dissented from the 5-4 ruling that upheld Trump’s order.

Justices occasionally recuse themselves because of apparent conflicts. Chief Justice William Rehnquist stepped aside from cases argued by San Francisco attorney James Brosnahan, who had testified against his confirmation. Justice Clarence Thomas bowed out of a successful 1996 sex-discrimination case against the all-male Virginia Military Institute because his son was a student there. And Scalia removed himself from a Bay Area man’s unsuccessful challenge in 2003 to the inclusion of “under God” in the Pledge of Allegiance because he had spoken publicly in favor of its inclusion.

The court has also taken a firm stance against conflicts of interest involving judges in lower courts. In 2009, the court said a West Virginia Supreme Court justice who had accepted campaign contributions from a coal mining company should not have taken part in a ruling overturning a $50 million damage award against the company because the public could no longer view him as impartial. The ruling required the state court to reconsider the case without the justice’s participation.

But Supreme Court justices rarely disqualify themselves because of positions they have taken before they joined the court.

In 1973, Rehnquist cast a deciding vote to uphold military surveillance of antiwar activists after speaking in favor of such surveillance as a Justice Department official under President Richard Nixon, who named him to the court in 1971. Rehnquist defended his participation, saying his previously stated opinions did not prevent him from considering the legal issues objectively, and noting that his disqualification would have prevented the court from deciding the case.

Kavanaugh, a former aide to President George W. Bush and a federal appeals court judge since 2006, could make a similar argument for participating in cases involving Special Counsel Robert Mueller’s investigation of whether Trump and his aides worked with Russia to undermine the 2016 presidential election, said Russell Wheeler, a judicial ethics specialist at the Brookings Institution.

Despite his role in the Starr investigation, Kavanaugh has written articles saying a president should be immune from criminal prosecution, investigation or court subpoena. He has also written judicial opinions taking a broad view of presidential power.

“He could say, ‘I wasn’t directly involved in the Mueller investigation, I have no personal interest ... and I can put these (writings) aside as many justices have in the past,’” Wheeler said.

One case on the court’s docket, Gamble vs. U.S., could affect Mueller’s investigation. The justices have agreed to reconsider past rulings that allow a state to prosecute someone who has been tried and acquitted of a similar charge in federal court, or vice versa.

If the court rules that such prosecutions violate the constitutional ban on double jeopardy, it could allow Trump to immunize associates from Mueller’s investigation by preventing states from prosecuting them after he pardoned them from federal charges.

The court is also considering a series of challenges to gerrymandering of election districts to favor either Republicans or Democrats, one of many disputes with partisan or ideological overtones that regularly come before the justices. It might be harder for Kavanaugh to argue that he is approaching such cases objectively after his public denunciation of the political left.

“It’s very difficult to believe, after (his Judiciary Committee testimony), that Judge Kavanaugh would be able to rule in a way that’s totally impartial and divorced from the depths of anger and resentment he expressed toward the left,” said Hofstra’s Sample.

Harvard law Professor Laurence Tribe, in a New York Times column this week, said Kavanaugh’s “partisan tirades” before the committee “disqualify him from participating in a wide range of the cases that may come before the Supreme Court.”

Richard Zitrin, who teaches legal ethics at UC Hastings College of the Law in San Francisco and formerly chaired the State Bar’s Ethics Committee, said he agrees with Tribe, but doesn’t expect Kavanaugh to go along.

In his testimony, Kavanaugh “started saying he would always remain impartial and proceeded to explain why he could never possibly be impartial,” Zitrin said. “But there is no recusal mechanism.

“I have no faith that the person I saw testify will ever do the right thing about recusing.”

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com

Twitter: @BobEgelko