The left faces an institutional barrier: The attention to Occupy Wall Street notwithstanding, news orgs tend to find right wing demonstrations of popular unrest inherently more newsworthy and deserving of sustained coverage than left wing ones.
True or false? Is there actual evidence on this score from, say, the past 30 years?
It seems to me that the nuclear freeze movement of the 80s got a fair amount of attention. So did the anti-globalization protests of the late 90s. And the Iraq war protests of the aughts. And various gay rights marches and protests. Maybe they've gotten less coverage than the tea party has gotten, but that's not immediately clear.
My sense is that when the left actually mounts a sustained popular movement, it gets a decent amount of coverage. Maybe not as much as we'd like, but that's probably what everyone who mounts a protest thinks. The problem, I suspect, isn't that popular movements of the left get ignored, but that the left hasn't been mounting any big, sustained popular movements lately. The fault, dear Brutus, etc. etc.