A new Gallup poll shows growing support for marijuana legalization, with 64 percent of Americans now in favor of the measure. The number is the highest level of support in nearly half a century of surveying adults on the issue, according to Gallup. Support has steadily increased in recent years, with the latest figure up 4 percentage points over last year and up 14 points from 2011. The poll also showed a majority of Republicans favoring legalization for the first time, with 51 percent expressing support. That number is up 9 percentage points from last year, according to Gallup.