Clarence Thomas, the hardline conservative supreme court justice, is facing calls for his recusal in the case over race-based affirmative action in college admissions that the court agreed to hear this week.

The case, which is being brought against Harvard and the University of North Carolina, is the latest potential conflict of interest involving Thomas and his wife Virginia Thomas. Ginni, as she is known, is a prominent rightwing activist who speaks out on a raft of issues that frequently come before the nation’s highest court.

A one-person conservative powerhouse, she set up her own lobbying company Liberty Consulting in 2010. By her own description, she has “battled for conservative principles in Washington” for over 35 years.

The challenge to the two universities’ race-conscious admissions policies is being brought by Students for Fair Admissions (SFFA). Its leader Edward Blum has been a relentless opponent of affirmative action and voting rights laws.

His argument that race-based affirmative action is a quota system that discriminates against Asian students is framed with the supreme court’s newly emboldened rightwing majority in mind. A central player in that new six-justice conservative supermajority is Clarence Thomas, who is the longest-serving of the justices and at 73 will be the oldest once Stephen Breyer retires.

Justice Thomas’s influence has soared in recent months with the rightward shift of the court following Donald Trump’s three nominations, to the extent that some pundits now dub him the unofficial chief justice of the court.

SFFA’s lawsuit seeking to strike down affirmative action has received the enthusiastic backing of the conservative National Association of Scholars. It filed an amicus brief in support of the suit, accusing Harvard admissions officials of being prejudiced against Asian students and stereotyping them as “uninteresting, uncreative and one-dimensional”.

Ginni Thomas sits on the advisory board of the National Association of Scholars. Observers are concerned that her position with a group that has intervened in the affirmative action case could present appearances of conflict of interest.

Noah Bookbinder, president of the government ethics watchdog Crew, told the Guardian that while supreme court regulations may not legally require Thomas to recuse himself, there were serious questions to answer.

“Ginni Thomas is an advisory board member of an organization that has taken a very specific position on a case in front of her husband. That will make it hard for the public to be confident that he’s going to be totally unbiased.”

Bookbinder said that in the circumstances “the better course of action would be for him to recuse or for her to cease her involvement in that organization.”

The potential appearance of a conflict of interest over the Harvard case was noted in a recent investigation by the New Yorker reporter Jane Mayer that takes a deep dive into the overlapping interests of the couple. The article chronicles in devastating detail the many instances where Ginni’s political activism appears to present problems for the image and integrity of the court.

“Ginni Thomas has held so many leadership or advisory positions at conservative pressure groups that it’s hard to keep track of them,” Mayer concluded. “Many, if not all, of these groups have been involved in cases that have come before her husband.”

In the most troubling recent instance, Ginni Thomas lent her voice to Trump’s big lie that the 2020 presidential election was stolen from him. She was vocal on the subject in the buildup to the violent insurrection at the US Capitol on January 6 last year that led to the deaths of five people and left more than 100 police officers injured.

On the morning of the January 6 itself, Mark Joseph Stern of Slate reported, Thomas posted on her Facebook page words of encouragement for the “Stop the Steal” marchers in Washington. “LOVE MAGA people!!!!”, she said., “GOD BLESS EACH OF YOU STANDING UP or PRAYING!”

Soon after the insurrection, Thomas was forced to apologise to her husband’s former supreme court law clerks for comments she made privately to them that appeared to lament Trump’s defeat in the 2020 election. The remarks were sent to a private email list called “Thomas Clerk World”.

In the emails, disclosed by the Washington Post, she wrote: “Many of us are hurting, after leaving it all on the field, to preserve the best of this country. I feel I have failed my parents who did their best and taught me to work to preserve liberties.”

An even more direct intervention in the politics surrounding Trump and the big lie was made last December when Thomas joined 62 other influential conservatives in signing an open letter to the leader of the Republicans in the House of Representatives, Kevin McCarthy. It urged him to expel the Congress members Liz Cheney and Adam Kinzinger from the Republican party.

Their sin, the letter writers opined, was to serve on the House committee investigating the January 6 insurrection. They described the committee as an “overtly partisan political persecution that brings disrespect to our country’s rule of law [and] legal harassment to private citizens who have done nothing wrong”.

Since the Capitol insurrection, the Department of Justice has arrested more than 725 defendants in relation to the storming of the building. Federal prosecutors have charged 225 with assaulting, resisting or impeding police officers, including over 75 charged with using a deadly or dangerous weapon or causing serious bodily harm to an officer.

Last week the supreme court rejected attempts by Trump to block the January 6 committee from acquiring his White House records from the time of the attack. There was only one dissent from the bench to that 8-to-1 decision: it came from Clarence Thomas.

“Ginni Thomas’s activities are unprecedented in supreme court history in terms of a spouse engaging in issues that are constantly before the court,” said Gabe Roth, executive director of Fix the Court, a non-partisan group which advocates supreme court reform. “The appearance of impropriety is in itself impropriety – all the supreme court has is the trust of the public, and once you chip away at that you are in trouble.”

Roth added that Thomas’s comments in the days before January 6 were clearly problematic given her husband’s vote on the Trump documents. “It’s possible that the January 6 committee has emails between Ginni Thomas and administration officials from that day or the days leading up to it given how vocal she was. That’s definitely a place where Justice Thomas should have recused himself.”

Should the rightwing majority around Thomas use its newfound muscle to ban affirmative action, as is widely predicted, it would mark the negation of more than 30 years of settled constitutional law on the matter. What lies ahead bears strong resemblance to Roe v Wade, the landmark 1973 ruling that made abortion legal which the court is probably poised to weaken or even overturn outright.

Mayer points out in the New Yorker that an amicus brief was filed in the supreme court case challenging Roe by Robert George who also sits on the advisory board of the National Association of Scholars alongside Ginni Thomas.

Roth told the Guardian that a simpler solution to the full recusal of Clarence Thomas from the affirmative action case might exist. That would be to remove the National Association of Scholars’ amicus brief.

“There is an easy way to deal with this perceived conflict of interest – strike the amicus brief,” he said.

It is established practice in all federal appeals courts, though not in the supreme court, that amicus briefs brought by anybody with a connection to a judge hearing a case are routinely thrown out.

The president of the National Association of Scholars, Peter Wood, told the Guardian that he knew of no conflict of interest relating to Thomas’s position on the advisory board. “Ms Thomas’s role is to provide advice to NAS in response to questions I put to her about NAS policy and initiatives. I have never discussed with her any NAS matter that was likely to come before the supreme court,” he said.