He was a member of the PSIN (Socialist Party of the National Left) until 1969, when the British historian Eric Hobsbawm supported his entrance to Oxford . He had close links with Jorge Abelardo Ramos, the founder of the PSIN, although he declared in 2005 that the latter then evolved in a direction he did not appreciate . In the same interview, he stated that he came from a Yrigoyenista family, and that the peronist politician Arturo Jauretche, a strong opponent of Justo's dictatorship during the Infamous Decade of the 1930s, was a close friend of his father .

Laclau's most important book is Hegemony and Socialist Strategy, which he co-authored with Chantal Mouffe. Their thought is usually described as post-Marxist as they were both politically active in the social and student movements of the 1960s and thus tried to link working class and new social movements. They rejected Marxist economic determinism and the notion of class struggle being the crucial antagonism in society. Instead they urged for radical democracy of agonistic pluralism where all antagonisms could be expressed.

“The Post-Marx of the Letter,” by Warren Breckman, in After the Deluge: New Perspectives on Postwar French Intellectual and Cultural History, ed. Julian Bourg. New York, 2004, 73-100.

"Laclau and Mouffe: The Radical Democratic Imaginary," by Anna Marie Smith. London, 1998.