When no major parties agreed to take him on as a presidential candidate in 2018, Jair Bolsonaro found a home in the tiny Social Liberal Party (PSL). To the disbelief of the political establishment, Mr. Bolsonaro won the presidency by a wide margin — and became 2018’s biggest kingmaker, paving the way for several of his little-known party colleagues to win their races for governor and Congress. The PSL went from being a small group with eight seats to the second-largest bench in the lower house.
His stellar electoral performance gave Mr. Bolsonaro the impression that the PSL...
