The chainsaw-wielding libertarian president of Argentina, Javier Milei, appears to be on the verge of getting his reform program through the legislature. This is not to discount the challenges ahead. The chance for a win, though, comes despite a wave of violent protest that erupted on the streets of Buenos Aires — a reflection of what Mr. Milei calls a bid by a corrupt political “caste” to thwart his mandate to revive Argentina’s economy.