However, AP-NORC asked a follow-up question that found a considerable amount of nuance in Americans' support marijuana legalization. Twenty-four percent of legalization supporters said marijuana should be made available "only with a medical prescription." Another 43 percent said there should be "restrictions on purchase amounts." And one-third of legalization supporters said there should be "no restrictions" on purchase amounts.
"This is yet another demonstration of just how ready Americans are for the end of marijuana prohibition," said Tom Angell of the Marijuana Majority, a marijuana reform group. "The growing level of support for legalization that we see in poll after poll is exactly why we're now in a situation -- for the first time in history -- where every major presidential candidate in both parties has pledged to let states set their own marijuana laws without federal interference."
Marijuana legalization is particularly popular among Democrats (70 percent support) and independents (65 percent). Nearly half (47 percent) of Republican voters support legalization as well.
There is a considerable age gap on the question. Eighty-two percent of 18-to-29 year olds support legalization, compared to only 44 percent of those aged 60+.
The survey comes at a potential tipping point for drug reform. Next month, the United Nations will hold a special session in New York to re-evaluate the state of international drug laws. Many researchers and public health experts have been encouraging the UN to take a less-punitive approach to drug policy. Yesterday, a group of medical and public health experts urged governments to decriminalize all drug use and experiment with regulated drug markets in some cases.
Here in the U.S. it's likely that voters in a number of states, including California, Nevada, Arizona and Massachusetts, will consider whether to legalize recreational marijuana at the ballot box this fall. And Vermont's legislature may opt to legalize marijuana before then.
And just last week, the U.S. Supreme Court tossed out a lawsuit against Colorado's marijuana regulatory regime brought by two neighboring states. Marijuana policy reformers say the decision gives some breathing room to other states considering legalization experiments.
Still, the AP-NORC survey numbers show the support for legalization is by no means uniform. Kevin Sabet of Smart Approaches to Marijuana, a group that lobbies against marijuana legalization, said in an email that given that nearly a quarter of marijuana legalization supporters only want to see it authorized with a doctor's prescription, that "does not show strong support for legalization at all." He notes that even under current medical marijuana laws, doctors aren't even able to write prescriptions for medical marijuana -- they can only issue "recommendations."
Previous Gallup surveys have not delved into the limits on support for legalization in the same way, so it isn't possible to compare those numbers with previous data.
But the survey is still likely to put some wind at the back of reformers hoping for victories on marijuana this year. And the growing levels of public support for legal marijuana -- up from 44 percent at the start of the Obama administration -- mean that the next president and Congress may face more pressure to make changes to marijuana law at the federal level.