“This issue is breaking out in a remarkably rapid way now,” said Ethan Nadelmann, executive director of the Drug Policy Alliance. “Public opinion is changing very, very rapidly.”

The shift is widely described as generational. A Gallup poll in October found 44 percent of Americans favor full legalization of marijuana — a rise of 13 points since 2000. Gallup said that if public support continues growing at a rate of 1 to 2 percent per year, “the majority of Americans could favor legalization of the drug in as little as four years.”

A 53 percent majority already does so in the West, according to the survey. The finding heartens advocates collecting signatures to put the question of legalization before California voters in a 2010 initiative.