Brazil’s largely conservative congress has approved a bill reducing the prison sentence of the far-right former president Jair Bolsonaro, who was convicted last year of attempting a coup.

The bill had initially been passed by congress in December, but president Luiz Inácio Lula da Silva vetoed it in January in a symbolic move marking three years since Bolsonaro supporters ransacked the capital, Brasília.

In a session on Thursday, the lower house overturned the veto with 318 votes, well above the 257 required, and the senate followed by 49 votes, with 41 needed.

If confirmed by a supreme court justice, Bolsonaro’s sentence would fall from 27 years and three months to 22 years and one month. Another significant change would be the time served in a closed regime, which could drop from what legal experts estimate at between four and six years to between two and four years, meaning the former president could move to an open regime as early as 2028.

It marked a second major blow in less than 24 hours for the leftwing president, who will seek re-election in October in what is expected to be a tight race against one of Bolsonaro’s sons, the senator Flávio Bolsonaro, who took part in the vote.

On Wednesday night, Lula suffered a historic defeat when he became the first president in more than 130 years to have a nominee to the supreme court rejected by the senate, the lawyer Jorge Messias.

Although both the overturning of the veto and the rejection of the court nominee had in some form been anticipated, they are being widely interpreted in Brazil as further evidence that Lula, who in polls appears virtually tied with Bolsonaro’s son, will face a difficult election.

Despite the overturning of Lula’s veto, the reduction of Bolsonaro’s sentence, as he remains under house arrest, will not be automatic; his lawyers will need to file a request for a sentence review with the supreme court.

The new law reduces not only his sentence but also that of about 280 others convicted over the attempted coup to overturn the result of the 2022 election, when the incumbent Bolsonaro was defeated by Lula.

Lula has not yet commented on the decision. When he vetoed the bill in January, he said reducing sentences for an attempted coup would encourage similar crimes in the future. “This man [Bolsonaro] must remain in prison,” he said.

The president has also not announced whether he intends to put forward a new nominee for the vacant seat on the supreme court.

His previous nominee, Messias, the government’s current solicitor general, delivered an anti-abortion speech during his senate hearing and was seen as an attempt to appeal to evangelical voters, who make up 26.9% of the population and have overwhelmingly backed Bolsonaro.

The senate had not rejected a presidential nominee since 1894, and the decision is widely attributed to an agreement between the senate president, Davi Alcolumbre, and the opposition led by Flávio Bolsonaro, as well as to retaliation for Lula’s refusal to nominate a candidate backed by Alcolumbre.

The senate president has reportedly told close allies that he will only allow a new confirmation hearing after the election. If Flávio Bolsonaro were to win, and given the number of justices expected to retire in the next four years, along with two previously appointed by his father, the Bolsonaro family could secure a majority of six out of the court’s 11 justices.