National Social Liberal Party presidential candidate Jair Bolsonaro greets supporters as he gets a shoulder ride from a member of his security detail, in Brasilia, Wednesday, Sept. 5, 2018, a day before he was stabbed. He remains hospitalized. (Eraldo Peres/AP)

Brazilian voters go to the polls next month to elect a new president. Right-wing firebrand Jair Bolsonaro of the fringe Social Liberal Party is ahead in the polls, following government corruption scandals that have tainted the mainstream parties, a paralyzing truckers’ strike, and protests over the imprisonment of former president Luiz Inácio Lula da Silva, known as Lula. The campaigns are only beginning to heat up. An apparently unstable man recently stabbed Bolsonaro during a campaign rally, threatening his life and taking him off the campaign trail for now, but he remains popular.

Commentators are comparing Brazil’s political crisis with Brexit, the election of Donald Trump in the United States and populist movements elsewhere. Fear, fake news and acrimonious polarization, so the story goes, are driving an angry electorate into the arms of a dangerous and extreme candidate.

But we do not yet know whether Bolsonaro will win. Comparisons with Trump and Brexit are overblown. Here’s why.

1. Fragmented parties generate both extremist and centrist candidates

When British voters went to the polls over Brexit in 2016, they had only two choices: Support or oppose keeping Britain in the European Union. Similarly, voters in 2016 chose between only Trump and Hillary Clinton for president. In both cases, each side perceived the other as extreme and repugnant. Voters quickly polarized. The outcome in both cases was close — in the United States, so close the winner of the popular vote did not become president, given how those votes were distributed.

But Brazil’s party system allows many choices, not just two. In the latest Datafolha Institute poll, Bolsonaro leads with 26 percent of intended votes, followed by center-left Ciro Gomes with 13 percent, Lula’s handpicked successor Fernando Haddad also with 13 percent, center-right candidate Geraldo Alckmin with 9 percent, center-left Marina Silva with 8 percent, and several others with even lower single-digit support.

Apart from the extreme-right Bolsonaro and leftist Haddad, all the leading candidates are center-left or center-right. Given the consistently fractured poll numbers, there is a strong chance at least one of the top two candidates for the late-October runoff will be a centrist.

2. Electoral rules matter. A lot.

In the United States, a candidate rejected by a majority of voters can win a majority of the votes in the electoral college, as both Trump and George W. Bush can attest. Brazil’s electoral rules are different. In its two-round electoral system, much like the one used in France, a candidate needs a majority — not just a plurality — of valid votes to be elected in the first round. If no candidate gets more than 50 percent of the first-round vote, the top two candidates compete in a second round, the runoff.

Since the parties are so fragmented, presidential candidates are unlikely to emerge from the first round with a clear victory — unless they form large and often ideologically diverse coalitions. Brazil’s electoral laws give candidates strong incentives to forge such coalitions — because the government offers free TV and radio time to candidates based on the share of seats their coalition has in Congress. Such coalitions tend to screen out extremist candidates who do not want to compromise.

If an extremist candidate does make it to the second round, he or she is less likely to win in the runoff. That is because by the time of the runoff, non-mainstream candidates will usually have alienated a substantial share of voters — voters who then gravitate toward the other, more centrist candidate. Brazil’s electoral rules thus promote mobilizing moderate voters by moving to the political center.

That is what happened in the French presidential elections of 2002 and 2017: Far-right candidates made it to the second round — and were then soundly defeated by centrists as voters united against the threat of extremism.

3. Lula’s Workers’ Party is not a cohesive, extreme coalition

Many believe Brazilian voters are divided between left-wingers who strongly support Lula’s Workers’ Party and right-wingers who strongly reject it. That is not exactly accurate.

Recent research shows voters who oppose the Workers’ Party are ideologically diverse. Some of them are conservatives, but others are center-left voters who support moderates like Silva and Gomes. In the United States, the ideological distance between Democrats and Republicans has increased over time. Things are different in Brazil’s multiparty system. There the top two vote-earning parties in every presidential race since 1994 — Lula’s Workers’ Party and Alckmin’s Social Democratic Party — have become all but ideologically indistinguishable.

What’s more, no presidential candidate lacking the support of a competitive pre-electoral coalition has ever been elected, with the exception of Fernando Collor in 1989. In those elections, voters considered Lula the “extreme” candidate from the left. Then-newcomer Collor, seen as more presentable and sensible, was preferred by the financial markets and the middle classes. Once he reached the runoff against Lula, large traditional parties quickly threw their support behind Collor — and put him over the top.

Bolsonaro has adopted an aggressively anti-establishment rhetoric that puts into question his willingness to share power with Congress. If he reaches the runoff, Brazil’s pragmatic, office-seeking parties may well prefer to back a candidate who is more eager to strike a bargain.

So what will become of Lula’s supporters? When included in the polls, the former president — even after being jailed for corruption — was leading with an impressive 39 percent. Now that the Workers’ Party has named Fernando Haddad as Lula’s substitute, it is not clear whether Lula’s voters will transfer to Haddad.

The coming Brazilian elections and the recent U.S. and U.K. experiences do share a common theme: The “outsider” option seems particularly attractive to many citizens. In Brazil, the “outsider” candidate will probably make it to the second round. But the nation’s constraints on extremists suggest whoever else reaches that round will be Brazil’s Jacques Chirac or Emmanuel Macron.

Felipe Krause is a Brazilian diplomat and political scientist.

André Borges is a professor of political science at the University of Brasília.

Opinions expressed here belong solely to the authors.