Brazil heads to the polls Sunday in one of the tightest and most consequential elections in its modern history, with President Luiz Inácio Lula da Silva, 80, fighting for a fourth term against Senator Flávio Bolsonaro, 45, the son of an ex-president now serving a 27-year prison sentence for attempting to overturn the 2022 election.

Both campaigns held their traditional closing pushes in São Paulo state over the election-eve weekend, drawing large, color-coded crowds — Lula's supporters in Workers' Party red, Bolsonaro's backers in the green and yellow of the national flag — as each side worked to turn out every last vote in a race pollsters have called essentially tied for weeks.

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Flávio Bolsonaro stunned forecasters by edging out Lula in the October 4 first round, 47% to 45%, defying pre-election polling. The latest Datafolha survey, taken October 6-7, had him ahead 49% to 45% heading into the runoff — a gap within the poll's margin of error. His father, Jair Bolsonaro, is barred from running after his conviction for plotting a coup following his 2022 defeat; the younger Bolsonaro has carried his movement forward while facing his own corruption probe over financing of "Dark Horse," a biopic about his father bankrolled by a jailed banker at the center of one of Brazil's biggest financial scandals.

"This country cannot lose its democracy," Lula told supporters at a recent São Paulo rally, framing the runoff as a referendum on Brazil's institutions.

Washington looms over the race. President Donald Trump has used tariffs and sanctions against Brazil over Jair Bolsonaro's prosecution and has said he is watching the vote "very closely," though he has stopped short of endorsing Flávio Bolsonaro. Lula has repeatedly warned Trump not to "meddle" in the vote, while Bolsonaro rallies have featured large American flags and imagery of Trump alongside the candidate.

The campaign has been dominated more by scandal and personal insults than policy: Lula has dismissed his rival as "a nobody," while Bolsonaro has branded the incumbent "incompetent." Lula is campaigning on welfare programs credited with lifting millions out of poverty, falling inflation and unemployment, and sharply reduced Amazon deforestation during his current term — though voters cite the high cost of living and crime as his biggest vulnerabilities. Bolsonaro is running on hardline crime policy and fiscal austerity amid rising public debt.

Nearly 160 million Brazilians are eligible to vote Sunday, also choosing new lawmakers, governors and senators in races that will shape Congress for the next four years. Whoever wins will be sworn in on January 5, 2027, in a result widely seen as a test of whether Latin America's largest economy joins a broader rightward shift across the region. Polls close Sunday evening local time, with a result possible within hours given Brazil's fully electronic vote count.