BRASILIA (Reuters) - Brazilian President Luiz Inacio Lula da Silva's 580-day stretch behind bars imbued him with a renewed sense of social justice, the leftist's allies and confidants said, convincing him of the need to prioritize ending poverty over boosting profits.

Lula takes office on Sunday for an unprecedented third term, capping a dramatic turnaround for one of the world's most enduring political leaders, who first ran for president in 1989.

Jailed for graft in 2018 - the year right-wing former President Jair Bolsonaro was elected - Lula's convictions were overturned in 2019, allowing him to oust Bolsonaro in October's election.

As he strives to unite a nation riven by economic woes, a bruising pandemic and Bolsonaro's far-right populism, Lula is looking to his prison days for inspiration, allies and confidants told Reuters.                                               

He learned from three failed presidential bids to tone down his leftist ideals and make peace with Brazil's powerful private sector during his 2003-10 presidency. But Lula 3.0 plans to double down on fighting poverty, ending hunger, and attacking racism, allies said, while also rewarding loyal Workers Party (PT) jail visitors with key cabinet positions.

"Prison reinforced the sense that he has a duty above all to the poor in Brazil," said Tarso Genro, a former PT governor of Rio Grande do Sul and a close Lula associate. "He went to prison strong and came out stronger."