PASOK was the ruling party when the economic crisis began, and it negotiated the first Greek bailout package with the European troika, which necessitated harsh austerity measures.

Papandreou, a powerful orator and charismatic leader, explicitly rejected the Venizelist ideological heritage of his father, and stressed the fact that he was a socialist, not a liberal.

At the November 1974 elections the Party received only 13.5% of the vote and won 15 seats (out of 300), coming third behind the centre-right New Democracy of Konstantinos Karamanlis and the Centre Union – New Forces (EK-ND) of Giorgos Mavros.

In the November 1977 elections, however, PASOK eclipsed the EK-ND, winning 93 seats by doubling its share of the vote and becoming the main opposition party in Greece at the time.

In the October 1981 national elections PASOK won a landslide victory with 48.1% of the vote, capturing 172 seats; it forming the first socialist government in Greece since 1924.

Although Papandreou had campaigned for withdrawal of Greece from NATO and the European Economic Community, after a strong request by the rest of the party members and its supporters,[citation needed] changed his policies towards both organizations.

For example, in 1985 he openly threatened Jacques Delors to veto the entry of Spain and Portugal in to the ECC to secure more monetary aid for Greece.

The former, because of the press’ reports of financial and corruption scandals that, implicated Ministers and, allegedly, Andreas Papandreou himself as well as because of fiscal austerity measures imposed after the Keynesian policies of the first term.

PASOK had changed the electoral law before the elections, making it harder for the leading party to form a majority government, so the legislature was deadlocked.

His governments carried through sweeping reforms of social policy by introducing a welfare state,[20] significantly expanding welfare measures,[21] expanding health care coverage (the "National Health System" was instituted, which made modern medical procedures available in rural areas for the first time,[22]) promoting state-subsidized tourism (social tourism) for lower-income families, and index-linking pensions.

[23] A number of other reforms were carried out in areas such as trade union rights,[24] shop closing and reopening times,[25] social security,[26][27] education,[28][29][30][31] health and safety,[32] and work councils.

[36] Various reforms were carried out in education, such as the modernization of university curricula and the introduction of new procedures for selecting and promoting faculty which involved greater participation by students.

[41] In January 1996 Andreas Papandreou retired after a protracted three-month-long hospitalization, during which he retained the role of Prime Minister; he died six months later.

He was succeeded by Costas Simitis, the candidate of the modernising, pro-European wing of PASOK (the so-called "modernizers", εκσυγχρονιστές eksynchronistes), who won an internal vote against Akis Tsochatzopoulos, a Papandreou confidant.

Although the Imia crisis had somewhat tarnished his image, the country's economic prosperity and his matter-of-fact administration won him the September 1996 general election with a 41.5% of the vote.

Under Costas Simitis' leadership, PASOK had two major successes: In September 1997 Greece won the right to stage the 2004 Summer Olympic Games and in 2001 it was confirmed that the country would be included in the Eurozone, for which it had failed to meet the convergence criteria in 1998.

Costas Simitis won another term in April 2000, narrowly winning with 43.8% of the vote and 158 seats: a substantial achievement for a Party which had been in power almost continuously for nearly 20 years.

Under the guidance of British and U.S. experts, the government intensified its efforts and finally, with a string of events starting at 29 June 2002, the 17N members were captured and put to trial.

The party members were expecting that Papandreou could reverse the slide in the opinion polls which saw the opposition New Democracy (ND), under Kostas Karamanlis, 7% ahead at the start of the year.

Although Papandreou reduced ND's lead in the polls to 3%, he was unable to reverse the view of the majority of Greek voters that PASOK had been in power too long and had grown lazy, corrupt and had abandoned the inclusive and progressive principles of economic parity on which it was founded.

ND had a comfortable win at the 2004 legislative elections held on 7 March 2004, placing the party in opposition after eleven years in office with 40.55% share of the vote and 117 seats.

Despite ND's falling performance in the 2007 legislative election, PASOK suffered a crushing defeat, registering 38.1% of the vote, its lowest percentage in almost 30 years, and 102 seats in the Hellenic Parliament.

However PASOK decided to help the formation of a government by joining with New Democracy (ND) as well as the Democratic Left (DIMAR) of Fotis Kouvelis in a coalition under Prime Minister Samaras.

[58][59] Five PASOK members of the Hellenic Parliament were expected to join the new party, including the former ministers Philippos Sachinidis and Dimitris Reppas.

[citation needed] On 30 August 2015, ahead of the upcoming September snap election, PASOK announced an electoral alliance with DIMAR, dubbed the Democratic Alignment (DISY).

[74] On 1 June 2019 former PASOK leader Evangelos Venizelos left KINAL, accusing Gennimata of turning the Movement into "SYRIZA's tail".

[84] In the 2024 European Parliament election, even though the party managed to come first in Lasithi and Heraklion, PASOK eventually came in third place, recording a 12,79% vote share.