LOS ANGELES — A growing majority of Americans, including Republicans, say marijuana should be legal, underscoring a national shift as more states embrace cannabis for medical or recreational use.

Support for legal marijuana hit 61 percent in 2018, up from 57 percent two years ago, according to the General Social Survey, a widely respected trend survey that has been measuring support for legal marijuana since the 1970s.

An analysis of the survey by The Associated Press-NORC Center for Public Affairs Research and the General Social Survey staff finds that increased backing of legalization cut across all age groups and political parties. The 2018 poll is the first in which a majority of Republicans support legalizing marijuana — 54 percent, up from 45 percent in 2016.

Among Democrats, 76 percent now favor legalization.

The rising support mirrors the evolving legal landscape across the country. Most Americans now live in places where marijuana is legal in some form, with 10 states allowing recreational usage and more than 30 allowing medicinal use.

The GSS asks about making use of marijuana legal, but does not specify whether it should be legal for recreational or medical use.

Support Strongest Among 18-to-34-Year-Olds

Legalization advocates say the increasing public support should prompt the U.S. government to reverse course. At the federal level, marijuana is categorized as a dangerous illegal drug, similar to LSD or heroin.

“Our time has come,” said Justin Strekal, political director of the National Organization for the Reform of Marijuana Laws, or NORML. “Never in modern history has there existed greater public support for ending the nation’s nearly century-long experiment with marijuana prohibition.”

Support for legalization is strongest among 18-to-34-year-olds, with nearly 75 percent favoring it.

But older Americans are taking a more favorable view, too. Forty-six percent of those 65 and older say marijuana should be legal, up from 42 percent in 2016.

Views on marijuana legalization have shifted dramatically: In the 1973 GSS, just 19 percent supported legalization.

The change in Americans’ views about cannabis can also be witnessed on the campaign trail. A growing list of Democratic presidential contenders want the U.S. government to legalize marijuana, including California Sen. Kamala Harris, a former prosecutor whose home state is the nation’s largest legal pot shop, and New Jersey Sen. Cory Booker, a prominent legalization advocate on Capitol Hill.

Support for legal pot has been gradually growing for years, but it has increased sharply since 2012, when Colorado and Washington state became the first states to legalize the recreational use of cannabis.