Di Rupo came in contact with the socialist movement for the first time during his studies in Mons, where he first obtained a master's degree and afterwards a PhD in chemistry.

He went during the preparation of his doctorate to the University of Leeds (United Kingdom), where his function was that of lecture member of staff in 1977–1978.

In 1991, Di Rupo was chosen as a senator, but shortly afterwards (1992), he took in the French-speaking community his first ministerial function in Education and later also Media.

After the federal and regional elections of June 1999 in which, due to the Dioxin Affair, the Christian-Democrats lost many of their votes, Di Rupo negotiated with the Flemish socialists of sp.a, the Liberals and Green Party to form a "purple-green" government.

[citation needed] As new president of the party, Di Rupo was forced to make a generation change within the PS and go down a new path.

During the regional and federal elections of 1995 and 1999, the PS lost many of its votes, partly because of corruption scandals in the 1990s (named Agusta-scandal and UNIOP-affair), in which the most prominent PS-politicians were involved.

Di Rupo realised that drastic action was required to regain the position of the PS.

By several measures, such as "Contrat d'avenir pour la Wallonie" (Contract for the Future of Wallonia) and a new generation of party leaders, by which Marie Arena was important, he tried to reassemble the left wing-forces around him.

In October 2005, he became Minister-President of Wallonia[8] after Jean-Claude Van Cauwenberghe resigned amid a corruption scandal, involving several members of Di Rupo's party.

[citation needed] In 2006 and 2007, Di Rupo and his party appeared unsuccessful in trying to clean out corruption.

The RTBF raised questions, however, about whether Di Rupo's limited fluency in Dutch would be a stumbling block in seeking that office; every prime minister since 1979 had been a Fleming.

[citation needed] In May 2011, he was appointed Formateur by King Albert II, which gave Di Rupo the task of forming a government.

[15] With Di Rupo's appointment, Belgium ended 589 days without a government, believed to be the longest such streak ever for a country in the developed world.