Michigan joined nine other states and Washington, D.C., in legalizing marijuana for adult recreational use. It's the first state outside of the West and Northeast to do so, and it reflects just how dramatically public opinion in America has shifted on marijuana. In just 10 years, legalization has gone from a fringe issue, attracting about 40 percent support, to a mainstream topic attracting vast bipartisan support.
The history of this shift is instructive. The conversation around marijuana started with compassion for seriously ill patients who benefited from the medical properties of marijuana. Activists started growing medical marijuana in the 1980s and '90s, in the context of the AIDS epidemic, to share it with patients who were wasting away and dying painful deaths.
When the George H.W. Bush administration shut down a program that had been allowing some access to cannabis in 1989, San Francisco activists pushed for a local ordinance to allow medical marijuana.
That led to California's Prop 215, the Compassionate Use Act of 1996, which opened the door to other states legalizing marijuana for therapeutic purposes.
Over time, stories about patients benefiting from cannabis humanized the issue and powerfully posed the question of why — of all substances — this one was prohibited.
The publication of data showing severe racial disparities in marijuana enforcement, with black people being several times more likely to be arrested for marijuana use than white people, despite comparable rates of use, also made it increasingly difficult to defend prohibition.
Legalization has received a further boost simply from the fact that it is working.
Opponents' worst fears have not materialized: Neither youth marijuana use nor the DUI rate has increased in states that legalized, according to our research.
Instead, in states where data are available, arrests are dropping, states are enjoying cost savings while filling their coffers with marijuana revenue, and regulators are putting in place strict measures to protect health and safety in a legal marijuana market.
As the Michigan vote indicates, the question is no longer whether to legalize cannabis: It is how to do it in a manner that repairs the many harms from decades of prohibition.