Stephen Breyer, the supreme court justice who announced his retirement this week, “did not want to die on the bench”.

So his brother, the federal judge Charles Breyer, told the Washington Post at the end of a momentous week in US politics.

Democrats, meanwhile, rejected Republican complaints that Joe Biden’s pledge to nominate the first Black woman to the court meant he was prioritising politics over qualifications, or endorsing racially based affirmative action, or that the new justice would be too liberal.

The Democratic chair of the Senate judiciary committee hinted at claims some criticism may be racially motivated, saying he hoped Republicans were not “doing it for personal reasons”.

Breyer’s decision to step down, at 83, gives Biden the chance to nominate a liberal replacement. The pick will not alter the balance of the court, which conservatives dominate 6-3 after Donald Trump capitalised on ruthless Republican tactics to install three justices in four years.

But progressives campaigned to convince Breyer to quit, many citing what happened when Ruth Bader Ginsburg died on the court in September 2020. Republicans who held the Senate confirmed her replacement – the hardline Catholic Amy Coney Barrett, nominated after Trump promised to pick a woman – before the November election.

Democrats should be able to confirm Biden’s pick without Republican votes but they face losing the Senate in November. With that in mind, the campaign to convince Breyer picked up speed. Breyer spoke about how the court should not be politicised but one activist, Brian Fallon of Demand Justice, told the Post: “You have to view this as a political fight. It’s not a legal fight.”

Charles Breyer told the Post his brother “was aware of this campaign. I think what impressed him was not the campaign but the logic of the campaign.

“And he thought he should take into account the fact that this was an opportunity for a Democratic president – and he was appointed by a Democratic president [Bill Clinton] – to fill his position with someone who is like-minded. He did not want to die on the bench.”

On Sunday, Dick Durbin of Illinois, chair of the Senate judiciary committee, told NBC’s Meet the Press: “I didn’t feel that external pressure was really helpful at all. [Breyer] had to make this decision. It is an important and timely decision in his life as to the right moment. And I didn’t want to push him, and I didn’t.”

But a congressman who campaigned for Breyer to retire, Mondaire Jones of New York, told the Post that though “people adore Ruth Bader Ginsburg … the fact is, due to decisions or non-decisions around retirement, made by her, we got Amy Coney Barrett.”

The Post said the White House did not pressure Breyer.

“None of the justices want to be told when to leave,” Charles Breyer said. “They want to decide themselves. And that, I think, the president and others recognised. It actually worked out.”

Republicans have signaled a willingness to make life uncomfortable for Biden’s nominee – as revenge for what happened to Brett Kavanaugh.

Trump’s second pick, replacing the retiring Anthony Kennedy, faced accusations of sexual assault. He vehemently denied them. Democrats prominently including Kamala Harris, then a California senator, vehemently attacked him. Harris is now vice-president, presiding over the 50-50 Senate with a vote to confirm Biden’s pick.

On Friday, the Republican senator Roger Wicker told Mississippi radio the Kavanaugh confirmation was “one of the most disgraceful, shameful things and completely untruthful things that [Democrats have] ever, ever done”.

Wicker also predicted that Biden’s nominee would get no Republican votes. He said so in part because the GOP expects a more progressive choice than Breyer, who Wicker called a “nice, stately liberal”. But Wicker also complained about “affirmative racial discrimination [for] someone who is the beneficiary of this sort of quota”, at a time when the court seems poised to rule such practices unconstitutional.

The White House reminded Wicker of his unquestioning support for Barrett.

Speaking to ABC’s This Week, Durbin said Republicans should “recall that it was Ronald Reagan who announced that he was going to appoint a woman to the supreme court, and he did, Sandra Day O’Connor, and it was Donald Trump who announced that he was going to replace Ruth Bader Ginsburg with a woman nominee as well.

“African American women, if they have achieved the level of success in the practice of law and jurisprudence, they’ve done it against great odds. They’re extraordinary people … they’re all going to face the same close scrutiny.

“… I just hope that those who are critical of the president’s selection aren’t doing it for personal reasons.”

Tom Cotton, an Arkansas Republican senator, told Fox News Sunday Republicans would probably not support Biden’s pick “because I’ve seen dozens of his nominees to the lower courts and they’ve almost to person been leftwing ideologues”.

Cotton also complained about Democrats’ treatment of Clarence Thomas, who was accused of sexual harassment in a stormy confirmation process, Biden playing a leading role as a senator from Delaware, in 1991.

Most expect Democrats to move quickly. Durbin told NBC: “A great deal depends on the nominee. If the person has been before the committee seeking approval for a circuit court, then the committee knows quite a bit about that person.

“If there are no new developments for someone who’s been before the committee in the previous year or two, it makes a real difference.”

A leading contender, Ketanji Brown Jackson, was confirmed to the DC appeals court last June with Republican support. She replaced Merrick Garland, Biden’s attorney general who was nominated to the supreme court by Barack Obama in 2016 but blocked by Republicans.

“I can just say this,” Durbin said. “It’s going to be fair, it’s going to be deliberate and we’re going to be timely about it too. This is a lifetime appointment to the highest court in the land. We should take it seriously.”