In 1969, he was brought in from relative obscurity by Rafael Paasio, a former Prime Minister of Finland, to assume the influential post of party secretary, despite not having much experience of national politics.

[3] However, other historians have disputed this, and while there was a list in a pro-Soviet newspaper of the candidates who should not be chosen as the party secretary, such as the right-wing social democrat Pekka J. Korvenheimo, there is no proof that the Soviets would have at this point particularly supported Sorsa.

[12][13] Sorsa is regarded as one of Finland's most influential prime ministers, making major contributions to schools and health care, and increasing social security for families with children and pensioners.

Infocracy challenges parliamentary democracy, is unintelligent and avoids discussing social problems, he said: it takes more interest in individual politicians than political issues and is never critical of its own actions.

In the 1970s, despite opposition from far-left parties, he championed a hard-won, free-trade agreement with the European Economic Community (EEC), which boosted ties between Finland and the countries of Western Europe.

In the late 1970s and in the 1980s the Socialist International had extensive contacts and discussion with the two leading powers of the Cold War period, the United States and the Soviet Union, on issues concerning East–West relations, arms control and Afghanistan.

They had several meetings and discussion in Washington, D.C., with President Jimmy Carter and Vice-President George Bush and with CPSU Secretaries General Leonid Brezhnev and Mikhail Gorbachev in Moscow.

[4] Ahtisaari was supported by a small but significant group of Finnish politicians who had long been hostile to Kalevi: Erkki Tuomioja, Lasse Lehtinen and Matti Ahde.