Gallup (h/t Law Enforcement Against Prohibition):
PRINCETON, NJ -- Gallup's October Crime poll finds 44% of Americans in favor of making marijuana legal and 54% opposed. U.S. public support for legalizing marijuana was fixed in the 25% range from the late 1970s to the mid-1990s, but acceptance jumped to 31% in 2000 and has continued to grow throughout this decade.
As you can see in this chart, support for marijuana legalization has never been stronger:
In the poll, most liberals (78%) and Democrats (54%) supported legalization, while moderates (46%) and independents (49%) were evenly split. Only conservatives (27%) and Republicans (28%) strongly opposed legalization.
The most important demographic breakdown was by age. 50% of 18-49 year olds supported legalization, compared to just 28% of those 65 and older.
The reason why those numbers are so important is straightforward: assuming today's 18-49 year olds maintain more or less the same attitude towards legalization 10 or 15 years from now, these numbers strongly suggest that marijuana legalization is no longer a question of if -- rather, it is now a question of when.