That's the point. I'd say the figure is closer to 80%. There are more stoners than ever before, and also more occasional users. And more than half are against abortion rights or at the very least, government/taxpayer/publicly funded abortions.
It's political suicide because when, inevitably, marijuana is legalized either in all 48 states or at the federal level, then it will no longer be a tipping point item to swing voters on the fence. The Dems will have one of their last items with bi-partisan support to run on. Gay marriage in 2015 was another one, and it's almost criminal that it got fully legalized federally before full recreational marijuana legalization, since it's far less controversial. Even most religious people don't care if people smoke pot.
If the main selling points are narrowed down to "tax da rich" and "fight teh global warming" then the left is screwed. Especially since the GOP is no longer the pro-war party.