The movement, known as Common Project since its inception, had taken a stance further to the left within the party as it opposed the political alliance with The Olive Tree, an association of center-left parties, being extremely critical of past centre-left governments, in particular the first Prodi government with Massimo D'Alema and Giuliano Amato.

The backers of the PCL believed that the future PD would be centrist and liberal and close to the interests of banks and corporations.

Regarding the Rainbow Left, they considered this coalition fundamentally social democratic and too close to the administration with only a pretension of revolutionary idealism and radicalism.

Further support come from the anti-globalization movements, groups opposing imperialism and those in favor of overthrowing the government in Israel (in particular the Palestine Forum) or protesting against the war.

In autumn 2006, the PCL together with other peace organizations and anti-imperialist participants in the protest against the military missions in Afghanistan and Lebanon (30 September) and in the national demonstration of anti-Israeli activity with Palestinian people, sponsored by the Palestine Forum.