Amid a looming third coronavirus wave, a stuttered vaccination effort, and unfavorable electoral polls, President Jair Bolsonaro is trying to muffle the sound of his growing opposition with the roar of motorcycle engines. In May, the far-right leader gathered tens of thousands of mostly unmasked bikers on the streets of Brasília and Rio de Janeiro for a series of noisy public rallies — much to the surprise to those outside of the pro-Bolsonaro social media bubble.
On June 12, Mr. Bolsonaro hopes to attract 1 million motorbikes to take to the streets of São Paulo in a show of strength. Organizers...