In 1965 the military government abolished the multi-party system and replaced it by a two party system. ARENA which was the government party and the MDB for the entire opposition. The majority of the politicians who joined ARENA had belonged to the UDN and an almost equal number came from the PSD .

The two party system turned into a trap for those in power. Elections became plebiscites in which people voted for or against the government. All nay votes went to the MDB. In an attempt to weaken the opposition all political parties were abolished and new organisations would need to have the word partido in their name.

ARENA had a bad reputation and so it tried to perform some window dressing and became the PDS . The PDS won the congressional elections of 1982 but in the gubernatorial elections held at the same time opposition parties made impressive gains.

The struggle for the presidency in 1984 led to a split in the PDS. This led to a new party the PFL that still plays a major part as one of the conservative parties in Brazilian politics. In the 2004 local elections the PFL finished fourth in number of votes.