Trends for legalizing cannabis

Nate Silver in his post Americans Growing Kinder to Bud brings us this pretty chart regarding polling data on marijuana legalization over the past 40 years.

It’s a fascinating chart. You see the clear temporary reversal of opinion trends during the Reagan “Just Say No” era, but since then the trend toward legalization has moved inexorably forward, even despite some of the most virulent anti-pot government propaganda during the past 8 years. (I credit the growing drug policy reform movement for defanging that particular effort).
Nate notes the political difficulties associated with legalization and says:

My guess is that we’ll need to see a supermajority of Americans in favor of decriminalizing pot before the federal government would dare to take action on it. If the upward trend since 1990 holds (and recall my earlier caution: it might not), then legalization would achieve 60 percent support at some point in 2022 or 2023. About then is when things might get interesting.

If marijuana criminalization was simply a matter of federal law, I’d agree. But the states add another element that could speed up the process in some ways (as more and more move to medical marijuana, decrim, or outright legalization, making federal law approach irrelevancy) or slow it down in others (some states may not be ready for legalization even in 15 years).
And I also think, as one commenter over there said, that the trend may not be flat – that we would be reaching a critical mass that would create a dramatic increase in support for legalization.