Brazilian investors and citizens alike are happily anticipating the arrival of “anybody but Dilma.” Since late January, despite the country’s crushing recession, Brazilian stocks are up more than 50% in dollar terms, inspired by the campaign to topple President Dilma Rousseff, who was impeached on Sunday by the lower house of Brazil’s Congress for allegedly violating financial responsibility laws.

Nations often break out of economic malaise after a crisis wakes up the populace to the need for change, and a charismatic reformer...