The practical problem has always been that those who should have been the vanguard for socialism -- workers in developed capitalist nations -- have been the rearguard, so to speak, with American workers being probably the most backward among the rearguard. Perhaps it is against today's leftist decorum to speak of anyone being politically backward, but it doesn't help us either to pretend not to notice what we are up against.
One naturally wishes that we were all on the same page politically, as it were, but that's not the case. In any social movement -- be it abolitionism, trade unionism, civil rights, anti-Vietnam War, feminism, GLBT liberation, disability rights, environmentalism, or whatever -- it's been always a minority who spearheaded organizing for progressive social change, gradually expanding the movement from the core of committed organizers ("cadres" if you will) outward to the (as yet unorganized) masses as much as possible. In no case the majority of the proverbial general public simultaneously jumped to a political cause.
Yoshie