The Leftwing Union for the Socialist Democracy was a Portuguese

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

 leftwing party founded in January of 1978. The party has its origins in the Socialist Culture Association - Worker Brotherhood, a socialist

Socialism

Socialism is an economic system characterized by social ownership of the means of production and cooperative management of the economy; or a political philosophy advocating such a system. "Social ownership" may refer to any one of, or a combination of, the following: cooperative enterprises,...

 organization and in groups of independent people linked to the Socialist Party

Portuguese Socialist Party

The Portuguese Socialist Party was a political party in Portugal.The party was founded in 1875. During its initial phase the party was heavily influenced by Proudhonism, and rejected revolutionary Marxism. The party suffered constant factional struggles...

.

The party participated in the legislative election of 1980

Portuguese legislative election, 1980

The Portuguese legislative election of 1980 took place on October 5.In January 1980, the Democratic Alliance, which had won the previous election, on December 2 of 1979, entered office with Francisco Sá Carneiro leading the government...

 in coalition with the Socialist Party

Portuguese Socialist Party

The Portuguese Socialist Party was a political party in Portugal.The party was founded in 1875. During its initial phase the party was heavily influenced by Proudhonism, and rejected revolutionary Marxism. The party suffered constant factional struggles...

 and the Independent Social Democratic Action in the Republican and Socialist Front

Republican and Socialist Front

Republican and Socialist Front was an electoral alliance in Portugal, consisting of the Socialist Party , Leftwing Union for the Socialist Democracy and Independent Social Democratic Action . FRS contested the Portuguese legislative election, 1980...

. In the subsequent elections, the party's members integrated the lists of the Socialist Party. In the Presidential election of 1986

Portuguese presidential election, 1986

The Portuguese presidential election of 1986 was held on January 26, the second round took place on February 16.This was closest presidential election ever held in Portugal and was won by the Socialist Mário Soares, who initially had no more than 5% at opinion polls.In first round was easily won by...

 the UEDS members split, one part supporting Mário Soares

Mário Soares

Mário Alberto Nobre Lopes Soares, GColTE, GCC, GColL, KE , Portuguese politician, served as Prime Minister of Portugal from 1976 to 1978 and from 1983 to 1985, and subsequently as the 17th President of Portugal from 1986 to 1996.-Family:...

 and the other supporting Maria de Lurdes Pintasilgo

Maria de Lurdes Pintasilgo

Maria de Lourdes Ruivo da Silva de Matos Pintasilgo,GCC,GCIH ; was the first and to date only woman to serve as Prime Minister of Portugal, and the second woman to serve as Prime Minister in Europe, after Margaret Thatcher who had been firstly elected for this capacity in the same year.Maria de...

.

The party was disbanded in 1986 and some of its members joined the Socialist Party.