In this Dec. 19, 2023, file photo, Supreme Court justice Clarence Thomas and his wife Ginni Thomas attend a memorial service for former U.S. Supreme Court Justice Sandra Day O’Connor at the National Cathedral in Washington, D.C. (Mandel Ngan/AFP via Getty Images)

(WASHINGTON) — When all nine justices of the U.S. Supreme Court signed a new ethics code last year, each pledged to step aside from a case when “impartiality might be reasonably questioned” or when a justice or a spouse has a financial interest in the dispute.

That pledge, made amid ethics questions involving Justice Clarence Thomas and some of his colleagues — and which is not independently enforced — is now being put to the test in one of the court’s most high-profile and high-stakes cases in a generation, ethics experts say.

Former President Donald Trump this week will ask the justices to overturn a Colorado Supreme Court decision which said he had “engaged in insurrection” and is ineligible for the 2024 ballot under the Constitution’s 14th Amendment.

Thomas, the court’s most senior conservative, has unique association to events at the center of the ruling.

His wife Virginia Thomas, who goes by Ginni, is a longtime conservative activist and Trump booster who helped lead the “Stop the Steal” campaign to overturn results of the 2020 election and who attended the Jan. 6, 2021, rally near the White House but did not march on the Capitol.

“Ginni Thomas was a supporter of Donald Trump’s, from pretty early on in his campaign, and she has maintained that support even through today,” said Gabe Roth, executive director of Fix the Court, a judicial watchdog group. “And those attempts to overturn the election was what led to the insurrection, which is what led to Trump being kicked off the ballot in Colorado.”

The Colorado ruling cited Trump’s “direct and express efforts, over several months, exhorting his supporters to march to the Capitol to prevent what he falsely characterized as an alleged fraud on the people of this country.”

Leading legal ethics experts say the activities of Ginni Thomas pose a clear conflict of interest for her husband.

“This is the easiest recusal analysis case you could ever imagine,” said James Sample, a professor and judicial ethics expert at Hofstra University Law School.

“The question isn’t, should Ginni Thomas be allowed or not allowed to engage in political advocacy,” Sample said. “The question here is, should Clarence Thomas, when Ginni Thomas engages in that political advocacy, be allowed to rule on the legitimacy or illegitimacy of that advocacy.”

Top Democrats have implored Justice Thomas to step aside.

“I’m afraid Justice Thomas, through his family, has crossed that line and he should recuse himself so there’s no question or bias in his decision,” Senate Judiciary Committee Chairman Dick Durbin, D-Ill., told ABC News.

Eight Democrats on the House Judiciary Committee wrote directly to Justice Thomas last month urging him to sit out the case.

“It is unthinkable that you could be impartial,” they wrote. “Ms. Thomas, has shown a fervent bias in favor of Mr. Trump, and it is hard to believe that her bias has no impact on you.”

Justice Thomas has not responded to Democrats’ demands and has not said whether he’ll recuse from the case, but his defenders say the calls are nothing more than a political ploy.

“I think there are people who would like to see Justice Thomas not deciding this case, and therefore they’re going to attack him,” said Carrie Severino, a former Thomas clerk and president of Judicial Crisis Network, a conservative legal advocacy group.

“You can spin out a crazy story but why anyone might have some, you know, appearance of impropriety in the eyes of someone who is engaging in conspiracy theories,” Severino said, “but this has to do with what is a reasonable appearance of impropriety.”

Neither the justices nor their spouses are formally bound by the Supreme Court’s ethics code, and each justice gets to make recusal decisions on his or her own.

The Thomases did not respond to ABC News’ requests for comment.

Several of Justice Thomas’ allies suggested to ABC News that he is not likely to recuse from the Trump case. He has already participated in cases that directly or indirectly involved the 2020 election. In all but one case, he did not recuse.

“Her activity is her activity,” said Severino. “Completely apart from the fact that she isn’t, was not involved in anything illegal on that day at all, there’s the fact that she is her own person.”

Ginni Thomas has said she had no role in planning the Jan. 6 event and that she was “disappointed and frustrated that there was violence.”

In testimony before a congressional committee investigating the Jan. 6 capitol attack, Thomas insisted she does not discuss politics or cases with her husband as an “ironclad rule.”

“Whether or not Clarence and Ginni Thomas discussed these issues in the privacy of their own personal conversations is not the issue,” Sample said. “It’s in the public domain that this case can implicate Ginni Thomas in ways that are particularly important to her and thus derivatively important to Justice Thomas.”

Ginni Thomas’ battle for conservative principles as a political consultant has stretched more than 30 years and distinguishes her from other Supreme Court spouses.

“I don’t think there’s any peer, frankly, in terms of the political activism of Ginni Thomas, she stands alone,” said Roth.

After the 2020 election, Thomas immediately engaged top Republican officials to fight the results, according to messages reviewed by ABC News.

To then White House chief of staff Mark Meadows she texted: “Help this great president stand firm, Mark!! You are the leader, with him, who is standing for America’s constitutional governance at the precipice.”

Around the same time, dozens of emails obtained by congressional investigators show Ginni Thomas wrote to Republican legislators in Wisconsin and Arizona urging them to overturn the will of state voters.

Roth said Justice Thomas, at the very least, should offer an explanation of his decision not to recuse.

“It’s not sour grapes, it’s not enmity, it’s not racism. It’s the fact that your wife wanted to overturn the election, and we have a lot of cases dealing with that insurrection. Tell us why you’re not conflicted,” he said.

Ginni Thomas has not been charged with any crimes. Her attorney has said she fully cooperated with congressional investigators, and she is not named in their 845-page report on the Capitol attack.

Still, a majority of Americans — 52% in a Quinnipiac University poll — believe Justice Thomas should sit out cases involving the 2020 election. Nearly as many, 47%, believe his wife’s political activities pose a unique ethical problem.

The Republican front-runner’s Supreme Court appeal this week is likely not the only one the justices could soon hear with ties to fallout from the 2020 election.

Trump is also fighting for absolute presidential immunity in the Special Counsel case against him over alleged election interference.

“This Clarence Thomas scenario related to January 6th and all of the January 6th litigation coming so soon on the heels of the court ostensibly adopting a code of conduct, will, if nothing else, highlight the need for enforcement mechanisms to make the code meaningful,” Sample said.

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