 López worked as an analyst and consultant for the chief economist to the Planning Vice-President of Petróleos de Venezuela S.A. (PDVSA) between 1996 and 1999; he was a professor of Institutional Economy in the Economics Department at Universidad Católica Andrés Bello.López cofounded the political party Primero Justicia (Justice First) with Julio Borges in 1992.He later moved away from Justice First, having a more leftist-leaning political philosophy and created the Voluntad Popular party, a member of Socialist International.