In June 2020, hundreds of K-pop fans and TikTok users helped tank a campaign rally held by then-U.S. President Donald Trump in Tulsa, Oklahoma. The Trump campaign had fielded more than a million ticket requests, but only 6,200 supporters actually showed up — leading a slew of photos of Mr. Trump talking to a largely empty arena.
What happened was thousands of K-pop fan accounts had encouraged detractors of Mr. Trump to sign up for the rally and simply not show up.
Two years later, Brazilian voters are trying to pull a similar stunt against Jair Bolsonaro, their own far-right leader running for re-election. On Sunday, Mr. Bolsonaro’s Liberal Party is scheduled to hold its national convention in Rio de Janeiro, which will mark the official start of the president’s bid for...