At the center of a huge government crisis, who is Gustavo Bebianno?

The first genuine political crisis of the still-incipient Jair Bolsonaro government has a face and a name: Secretary-General of the Presidency, Gustavo Bebianno.

Having served as the temporary leader of Jair Bolsonaro’s Social Liberal Party (PSL) during last year’s elections, Mr. Bebianno is accused of sponsoring a scheme of dummy candidates, by which ersatz runners were given vast amounts of campaign funds, only to have that money channeled into companies connected to PSL members. The candidates themselves ended up with tiny voting numbers.

Mr. Bebianno was quick to deflect any blame for the scheme, claiming he did not know anything about the dummy candidates and pointing the finger at PSL founder and kingpin Luciano Bivar—who retook the party presidency in the wake of the election.

What was once a potentially controllable scandal turned into a ticking time bomb, thanks to the involvement of one of the president’s sons, Carlos Bolsonaro. After Mr. Bebianno told the press that things had been smoothed out with the government and he had spoken “three times” to Jair Bolsonaro that day, Carlos took to social media and inadvertently dropped a flaming rag...