A woman walks with a sign supporting legalizing marijuana during the Democratic National Convention on July 28, 2016 in Philadelphia. (Spencer Platt, Getty Images)

Gallup poll: Americans’ approval of marijuana legalization highest in history ahead of 2016 election

A new Gallup poll released Wednesday shows 60 percent of American adults now say that marijuana should be legal, the highest level of support in nearly a half-century of polling on the question.

The Gallup poll tracks closely with numbers from the Pew Research Center released last week showing 57 percent support for legalization.

When Gallup first asked about legalization in 1969 only 12 percent of Americans supported the proposition. Support rose briefly to 28 percent in the late ’70s, but languished in the low- to mid-20s throughout much of the ’80s and ’90s, as the federal war on drugs hit a fever pitch.

As Gallup notes, support for legalization has soared in the past decade among nearly every demographic group. Close to 80 percent of 18-to-34 year olds now favor legal weed, up from 44 percent in 2003 and 2005. Gallup finds that Americans age 55 and older are now the only age group with less than majority support for legalization.

Support for legalization has more than doubled among Republicans in the past decade, to 42 percent today. With 70 percent support, independents are the political group most likely to favor legalization, just edging out Democrats at 67 percent.

Gallup notes that “the transformation in public attitudes about marijuana over the past half-century has mirrored the liberalization of public attitudes about gay rights and the same-sex-marriage movement.”

This fall, five states will decide whether to join Colorado, Washington, Oregon, Alaska and D.C. in legalizing marijuana for personal use. Polling in those states shows that, while the legalization measures are slightly favored by voters, the margins are very close. Most polls in those states show that support for the legalization measures is currently coming in below Gallup’s 60 percent nationally.

This is because there’s a significant difference between support for marijuana legalization in the abstract, and support for a concrete ballot measure with a lot of nuts-and-bolts proposals for how marijuana legalization would be regulated and enforced. A voter might support the idea of marijuana being legal, for instance, but not like a law that could lead to an actual marijuana shop in their neighborhood.

Perhaps realizing that the argument against legalization per se is already a lost one, opposition campaigns are focusing on specific provisions within the ballot proposals that voters may object to. In California, for instance, opponents have been alleging (mostly without basis) that the marijuana law would allow pot ads to run during TV programs watched by children.

Opposition campaigns elsewhere, like Massachusetts and Arizona, have been making the arguments that legalization would lead to more drugged driving, or to more cases of marijuana poisoning among children.

As Gallup notes, the outcome of the November measures could have a transformative effect on the marijuana policy conversation going forward: “The percentage of Americans living in states where pot use is legal could rise from the current 5 percent to as much as 25 percent if all of these ballot measures pass.”

And according to Gallup, the real prize for legalization proponents is California: “If recreational marijuana use becomes legal in California this year, many other states will likely follow, because the ‘Golden State’ often sets political trends for the rest of the U.S.”

The latest polling out of California suggest that the legalization measure is leading by a two-to-one margin.