For the first time, a majority of Americans support legalizing marijuana use, according to Gallup.
The only problem is the people that support legalizing marijuana use are among the least likely to vote. 63% of 18-29 year olds support legalization, making them the 2nd most supportive group behind liberals, but only 49% of eligible 18-29 year olds voted in 2008. Among those 65+, only 31% support legalization but 70% of them voted in '08.
Politicians have to be responsive to the electorate, if they like it or not. The broader American public appears to support legalization, but right now the electorate doesn't. Until supporters of legalization vote their numbers and elect politicians favorable to the cause, lighting a joint will still be a crime.