Complex sentence: The last election, three and a half years before, in April 1976, was won by the Socialist Party under the lead of Mário Soares, who became the Prime-Minister of the 1st Constitutional government after the revolution.
Split into simpler sentences: The last election, three and a half years before in April 1976, was won by the Socialist Party and Mário Soares. He became the Prime-Minister of the 1st Constitutional government after the revolution.