This article in Think Progress brings up a few interesting points.

1) No presidential candidate in 50+ years has won without winning 2 of the 3 swing states (PA, FL, OH).

2) According to a Quinnipiac University Poll, 80+ percent of voters in these states support medical marijuana and 50+ percent in all 3 states are OK with recreational marijuana.

So TP suggests that presidential candidates might start thinking of marijuana reform as a main stream issue.