Spectres of the past
In Portugal, the long reign of the fascist Salazar government created a profound political vacuum and economic crisis, as all opposition was repressed or driven abroad and Portugese capitalism was attached surgically to the exploitation of the waning empire's outposts in Angola, Mozambique and to a lesser extent Portugese Guinea. A handful of oligarchs ran the Portugese economy by importing raw materials from the colonies, processing them in clapped-out Portugese factories, and selling the shoddy end-products to Portugese and the colonials, who were deprived of any alternative by an strict import restrictions and other autarkic measures.
Once guerrilla movements had made the Portugese presence in Africa unsustainable, Portugese society was bound to go into freefall, but the vaccum created by Salazar meant that it was the military, or rather a radical section of the military, which had to take the initial lead in overthrowing the regime. Sound familiar? Once the coup of 1974 had opened the floodgates of dissent and working class organisation, revolution began in earnest: workers occupied factories and organised soviets, small farmers seized land, and students took over their universities. The provisional government established in the aftermath of the coup was forced to pass all manner of progressive legislation, and to make way for the election of a Constituent Assembly. Tragically, though, the right was able to mobilise its forces and destroy the parrallel institutions that the insurgent workers and farmers had created, rolling back the revolution. It has been a different story, thusfar, in Venezuela, where the right-wing representatives of the national bourgeoisie failed in repeated attempts to destroy the Chavez government by illegal and electoral means, and have for the moment at least been reduced to a pathetic rump.
It'd be interesting to see someone do a detailed comparative study of the Portugese and Venezuelan revolutions and identify the key variables that account for their differing fortunes. For a detailed but accessible history of the revolution, see this article.