I really don't have enough knowledge of Portuguese politics for this. Could you tell us something about these four PMs?
Sure.
Mário Soares: 1st elected PM in democracy; His 2 terms as PM were marked by economic downfall and IMF bailouts; in 1977, after 2 tumultuous post revolution years, the economy was in pieces and the state didn't had money so, the government asked for an IMF loan. Soares also had to govern with the IMF in his 2nd term (1983-85); Nonetheless, during his 1st term, the National Heath Service was created and Portugal officially applied for the European Community.
António Guterres: Elected PM in 1995 after 10 years of PSD governments. During his term he continued many of the PSD government's economic policies, especially on privatization. At the same time, he created many social programs for the poor, in particular many state subsidies for people earning below the NMW. His tenure was also marked by foreign diplomatic efforts particularly on the East Timor crisis. By the beginning of his 2nd term, the economy started to fall and many corruption scandals plagued the PS. He resigned after a disastrous loss in the 2001 local elections.
José Sócrates: Elected in 2005, he is Portugal's most controversial PM till date. Although his term was marked by the modernization of public services and incentives for a more competitive economy, his tenure is also marked by many corruption scandals and sketchy deals that really hurt the economy. In 2011, he asked for a loan from the IMF, the EU and the ECB.
António Costa: Formed government after losing the 2015 elections with the, unprecedented, support of the CDU and BE. Although he says he has turned the page of austerity, many of his policies dispute that. Government spending and investment dropped in 2016 and continues very low during 2017. On the other hand, Costa didn't changed many economic policies of the former PSD/CDS government.