Jair Bolsonaro’s rise a portrait of strange times in Brazil

Forecasts made by political scientists seem to be even less accurate than those by weather reporters. And, as global warming has produced new, hard-to-predict effects, so has the rising radicalization of Brazil’s political environment. It has altered how voters choose their candidates, stripping pundits of any premonitory capacity.

The bipartisan dominance of the Workers’ Party and Brazilian Social Democracy Party (PSDB) over the past six presidential races made most political scientists expect more of the same. We were also wrong about the weight of television and radio political ads, thinking they would be as powerful as before, and that they would propel establishment candidates.

However, several structural and conjunctural factors have smashed these forecasts. The brutal erosion of the image of Brazil’s two main parties has been felt in this election. The Workers’ Party, despite having massive support with Lula, has seen understudy Fernando Haddad suffer from significant rejection rates (despite considerable initial growth). The PSDB, which since 2002 has been the anti-Workers’ Party, was trumped by a much more radical alternative – far-right Jair Bolsonaro.

TV and radio ads, which grew less and less important as social media took over, now seem all but buried. Mr. Bolsonaro has fewer than 10 seconds on traditional media channels – but that has proven to be...