Unfortunately, it couldn't happen up to now, that is because I have some doubts about it. I think troubles are mainly operational. If you makes a violent revolution, so you must use repression to keep power. Won't this create a "new class" that can destroy the socalism in the long run? And if you win a election, then you've accepted the "game rules" (this means capitalist order) and then it's difficult to build socialism while the communication means and economic power remain in private hands. So there must be an alternative, but none of us know it. I think we must pay attention to Hugo Chávez "democratic rupture". Neither he is a socialist nor his movement is based in working class mobilization, but the idea of winning a election and after this convocate elections for a constituent assembly could be a legitimate way to start socialist changes if the working class is properly organized.
Alexandre