Ginni Thomas, the wife of the supreme court justice Clarence Thomas, was accused of “undermining democracy” after it emerged that she emailed 29 Republican lawmakers in Arizona in her effort to overturn Joe Biden’s victory over Donald Trump.

The Washington Post had previously reported that Ginni Thomas sent emails pressuring two Arizona Republicans to reject Biden’s win and choose their own electors.

On Friday, the paper said Ginni Thomas emailed 29 individuals.

Thomas’s involvement in Trump’s attempt to overturn his election defeat, including events around the deadly Capitol attack, has been widely reported.

That has focused attention on her husband, a stringent conservative who has not recused himself from election-related cases.

When Trump tried to deny the House January 6 committee access to White House records, Thomas was the only justice to side with the former president. Texts from Ginni Thomas to Trump’s chief of staff were subsequently revealed.

Supreme court justices govern themselves in ethical matters. Activists and some Democratic politicians have therefore called for Thomas to resign or be impeached.

Only one supreme court justice has been impeached: Samuel Chase in 1805. He survived. But Chase was accused of “tending to prostitute the high judicial character with which he was invested, to the low purpose of an electioneering partisan” – a charge with strong echoes in the case of Clarence and Ginni Thomas.

The Post said that on 9 November, two days after the election was called for Biden, Ginni Thomas used “FreeRoots, an online platform intended to make it easy to send pre-written emails to multiple elected officials”, to send identical messages to 20 members of the Arizona House and seven state senators.

The emails urged the Republicans to “stand strong in the face of political and media pressure” and “fight back against fraud”.

On 13 December, the day before electoral college votes were cast, Thomas emailed 22 members of the Arizona House and one senator.

That message said: “Before you choose your state’s electors … consider what will happen to the nation we all love if you don’t stand up and lead.” It also “linked to a video of a man urging lawmakers to ‘put things right’ and ‘not give in to cowardice’.”

Proven fraud in the 2020 election is vanishingly rare. Regardless, Arizona Republicans pursued a controversial audit – which increased Biden’s margin of victory.

Ginni Thomas did not comment on the new Post report. Nor did the supreme court. Thomas has said her activism does not clash with her husband’s work.

Noah Bookbinder, president of Citizens for Responsibility and Ethics in Washington, or Crew, said: “We’ve now learned that Ginni Thomas’s role in pushing officials to overturn the 2020 election was significantly greater than we knew.

“Justice Thomas’s failure to recuse on cases about the 2020 election looks worse and worse. This undermines democracy.”

Pointing to Ginni Thomas’s position on the Library of Congress Trust Fund Board, to which she was appointed by Trump, Crew said: “Friendly reminder that Ginni Thomas has a government position and absolutely should not.”

News of the Arizona emails emerged in the aftermath of a dramatic primetime hearing staged by the House committee investigating January 6. Responding to the hearing, Trump repeated his lie about electoral fraud.

Amid growing calls for a criminal indictment against Trump, Wajahat Ali, a columnist and senior fellow at the Western States Center, which works to strengthen democracy, tweeted: “Democrats should aggressively put pressure on Clarence and Ginni Thomas.

“You have an extremist conservative duo working the courts and the rightwing activist machine to overturn our free and fair election.”