Brazil’s President Luiz Inácio Lula da Silva, a vocal critic of U.S. President Donald Trump, was reelected Sunday.

But the contest in Brazil that matters most to Washington, D.C., is the U.S. competition with China. As Newsweek wrote previously, Trump could theoretically win Brazil with a Bolsonaro presidency, but still ultimately lose the country to Beijing.

President Donald Trump claimed Monday that Brazil’s presidential election, which leftist President Luiz Inácio Lula da Silva won, looked like it was “rigged” without citing evidence.

Right-wing Senator Flavio Bolsonaro goes into Sunday’s runoff with a slight edge, having picked up 47% of ballots cast in the first round, while leftist Lula trailed with 45%.

Right-wing rival Flávio Bolsonaro said he would seek to annul the vote after Lula made a surprise comeback to win Brazil’s presidential run-off.

Here are the key things investors need to know to start the trading day.

Far-right senator banned from leaving country as supreme court judge’s ruling makes reference to money-laundering case

On Sunday, Brazilians will choose between a beleaguered left-wing incumbent and a right-wing challenger. Trade, security and democracy are on the table.

The 'Fast Money' traders talk Brazil-related stocks reacting to shock election results. Got a confidential news tip? We want to hear from you. Sign up for free newsletters and get more CNBC delivered to your inbox Get this delivered to your inbox,

Already the country's oldest president, Lula overcame ​a first-round loss to pull off a surprise runoff victory against Senator Flavio Bolsonaro on Sunday, securing 51.8% of votes and a record fourth term just two days before his 81st ‌birthday.