Final answer:
The main supporters of the populist Peronist movement in Argentina were the urban working class, rural peasants, and the rising professional middle class.
Step-by-step explanation:
The main supporters of the populist Peronist movement in Argentina were the urban working class, rural peasants, and the rising professional middle class. In the first few decades of the twentieth century, this middle class included first-generation immigrants from Europe who supported a new Radical Party. Peronism gained popularity among the masses in Buenos Aires due to Juan Perón's role as the Minister of Labor, where he favored the workers in labor negotiations. Peron was able to deliver on his promises of higher wages, better living conditions, and other improvements for workers, which further gained support for the Peronist movement.