After more than four decades of polling on the issue, Pew Research released a survey Thursday showing that a majority of Americans for the first time support legalizing marijuana.

In the poll, 52 percent of respondents said they favored marijuana legalization, versus 45 percent who said the drug should remain illegal. It's a sharp leap from just three years ago, when only 41 percent of respondents to a Pew poll said marijuana should be legalized.

Americans have grown more tolerant of pot in the past forty years — except for a brief regression in the 1980s amid a federal anti-drug campaign — with a significant turn coming in the past decade. In 2002, six in ten Americans opposed legalization according to a Pew poll, twice the number who said the opposite.

Part of what's driving the change is likely an increase in its usage. A record-high 48 percent of respondents to the Pew poll said they'd smoked marijuana, an eight-point increase since 2010.

Those findings bolster a plethora of other polls in recent years that have found support for legalization either at or just shy of a majority nationwide. A Quinnipiac poll last December found that 51 percent of registered voters supported legalization, while a CBS News poll from November showed the nation split dead-even at 47 percent.

As public opinion on the issue has changed, so, too, have states' attitudes.

Last year, Colorado and Washington became the first two states to legalize marijuana, while several other states have also decriminalized possession of small amounts of the drug. At the same time, eighteen states have legalized marijuana for medicinal purposes, according to

Whether that shift will translate to the federal level is less certain.

Rep. Jared Polis (D) of Colorado introduced a bill this year that would essentially legalize marijuana by removing it from the Controlled Substances Act, and have it instead be regulated by a renamed Bureau of Alcohol, Tobacco, Marijuana and Firearms. Though that bill has virtually no chance of passing, advocates believe that it's only a matter of time before shifting demographics make such a position politically feasible.

"[I]f you were surprised at how quickly marriage equality happened, get ready for another shock: Pot’s going to be legal too," says Hunter Walker, writing for Talking Points Memo. "The same demographic and cultural changes that propelled marriage equality to majority status are already pushing support for legal pot to the same place."

A detailed look at polling trends seems to bear this out. 

In 2011, the New York Times' Nate Silver compiled a trove of polls from Gallup and others, producing a regression-smoothed chart that showed support for legalization at a near-tipping point thanks to a generational divide on the issue.

But the legalization position should have something of a wind at its back because of generational politics. In the Gallup poll, there is a fairly sharp split between those who came of age in the 1960s, and those aged 65 and older — many of whom grew up in a generation when marijuana use was not common. Only 31 percent of the older group supports legalization now.

Meanwhile, support is as high as 62 percent among Americans under age 30, although there is some evidence that support for legalization can erode as people age and have children. [New York Times]

Editor's note: An earlier version of this article incorrectly identified as a pro-legalization site. We regret the error.