Leftist former President Luiz Inácio Lula da Silva won Brazil's presidential runoff Sunday, beating right-wing President Jair Bolsonaro with 50.90% of the vote, according to the country's election authority.

Why it matters: The results mark a stunning political comeback for Lula, who was sidelined during the last presidential election because of corruption convictions. But his victory will likely see an aggressive challenge by Bolsonaro, who has for months claimed without evidence that Brazil's electronic voting system can be manipulated.

• Lula told supporters in Sao Paulo that "Bolsonaro has not called me to recognize my victory, and I don't know if he will call or if he will recognize my victory," Reuters reports.
• As Sunday drew to a close, Bolsonaro had yet to publicly comment on the results — which showed he had garnered 49.10%, with 100% of the votes counted.

State of play: Lula, a former two-term president, was blocked from running against Bolsonaro in the last election due to his conviction charges. Those charges, however, were thrown out, paving the way for him to seek a third term.

• The 77-year-old leftist led Bolsonaro in the polls during the campaign. But Sunday's runoff was seen as a toss-up after polls underestimated Bolsonaro in the first round.
• Misinformation soared during the campaign, which also saw politically motivated violence.

Lula has vowed to prioritize the environment, including combating the deforestation of the Amazon, which hit a 15-year high under Bolsonaro.

• He's also promised to "rebuild and transform" the country, which has witnessed a decade-long economic slump made worse by the coronavirus pandemic.

What they're saying: President Biden tweeted his congratulations to Lula "on his election to be the next president of Brazil following free, fair, and credible elections."

• Biden added that he looked forward to "working together to continue the cooperation between our two countries in the months and years ahead."

The big picture: Many analysts said the world's fourth-largest democracy was on the line on Sunday, with voters choosing whether to cement Brazil's far-right path under Bolsonaro or return the country to the leftist policies it saw under Lula from 2003-2010.

• The return of Lula also comes as other countries in South America turn toward the left.
• Colombia elected its first leftist president earlier this year, and Chile and Honduras last year voted for left-wing politicians to replace conservative leaders.

Editor's note: This article has been updated with new details throughout.