Passage in California, where polls show it has wide support, would make pot legal along the entire West Coast and give momentum to efforts to lift the ban nationwide. The state, the most populous in the U.S. with 39 million residents, was the first to allow medical marijuana two decades ago. In all, nine states will consider marijuana-related ballot measures on Nov. 8, which could more than double the $7 billion market for pot products by 2020.

“If this passes in California, and particularly if it passes in the other four states, it’s lights out for marijuana prohibition,” said Troy Dayton, chief executive officer of The Arcview Group, an Oakland-based firm whose 550 investor members have poured $85 million into 131 cannabis companies.

Attitudes toward legalizing marijuana in the U.S. may have reached a tipping point. Opinion polls show a majority of Americans support it. That’s a dramatic shift from decades past — partly the result of a new generation reaching voting age and nearly half the adult population trying pot. Failed drug policies that jail nonviolent users and growing evidence that it’s less harmful than cigarettes and alcohol have fueled calls for a change.