Complex sentence: In an extraordinary Congress of the MLSTP held in May 1998, Manuel Pinto da Costa was elected unopposed as president of the party, a post that he held until February 2005, when a successor, Guilherme Posser da Costa, was elected.
Split into simpler sentences: In an extraordinary Congress of the MLSTP held in May 1998, Manuel Pinto da Costa was elected unopposed as president of the party. He held this post until February 2005, when a successor, Guilherme Posser da Costa, was elected.