A majority of American adults think marijuana should be legalized, a poll released Thursday by the Pew Research Center finds. While 52 percent were pro-pot legalization, 45 percent of respondents were opposed to legalization.

"For the first time in more than four decades of polling on the issue, a majority of Americans favor legalizing the use of marijuana," Pew said in a statement posted online.

Sixty-five percent of adults between the ages of 18 and 32 support marijuana legalization, Pew said. Just five years ago the polling company found that 36 percent of voters in that age group supported legalization.

"These results do not just represent a tipping point," said Marijuana Policy Project political director Steve Fox in a statement. "With support for legalization among people under the age of 50 at close to 60 percent, this is more like the tip of the iceberg. Elected officials across the country need to listen to the people."

The poll also asked respondents if they had ever tried marijuana; 48 percent indicated that they had, but only 12 percent said they did so in the past year.

Pew also found fewer people – 38 percent – thought marijuana was a "gateway drug," while a 32 percent minority believed it is morally wrong to use the drug.

Pew Polling Data on Marijuana Legalization

1969* 1991 2002 2011 2013 Percent supporting legalization 12 17 32 45 52 Percent opposing legalization 84 78 61 50 45

*Gallup poll

According to Pew, 72 percent of respondents said the enforcement of anti-pot laws "cost more than they are worth," with 60 percent opposed a federal crackdown on states that have legalized marijuana.

Independent voters were the most supportive of marijuana legalization, at 60 percent, followed closely by Democrats, at 59 percent. Self-identified Republicans were, as a whole, more likely to oppose legalization, but a sizeable 37-percent minority indicated support for legalization.

"Not too long ago, it was widely accepted in political circles that elected officials who wanted to get re-elected needed to act 'tough' on drugs and go out of their way to support the continued criminalization of marijuana," recalled Tom Angell of Marijuana Majority in a statement released Thursday.

"The opposite is quickly becoming true," noted Angell, formerly spokesman for the group Law Enforcement Against Prohibition. "A majority of Americans support legalizing marijuana, and you're going to start seeing more politicians running toward our movement instead of away from it, just as we've seen happen with marriage equality recently."

In November voters in Washington state and Colorado approved marijuana legalization initiatives. It is currently legal to possess and smoke small quantities of the drug in those states, and the Obama administration has made no overt efforts to waft marijuana back into illegality. Since the historic votes, legislators in nine states have introduced legalization bills.

The evolution of public opinion on marijuana legalization mirrors the national pivot in favor of legalizing same-sex marriage. According to Pew, a majority of voters have supported gay marriage since 2011.

The marijuana legalization poll surveyed 1,501 adults March 13-17, 2013. Its calculated margin of error was 2.9 percentage points.