The PSD was the most important Brazilian political party during the 1945–1964 democratic period, electing Presidents Eurico Gaspar Dutra in 1945 and Juscelino Kubitschek in 1955.

It was dominated by executives appointed by the Getúlio Vargas regime and was therefore strongly interwoven with the state apparatus.

They therefore supported the military coup d'état on 1 April 1964, making an important contribution to the success of the overthrow.

A few elements of the PSD's right wing joined the pro-government National Renewal Alliance Party (ARENA).

It was based in the rural center-west and led by Ronaldo Caiado, leader of the right-wing landowners' association União Democrática Ruralista.