First, there's a difference between 'favored by less than 50% of the population' and 'fringe position'. If it's that popular already, your work is almost already done. And I don't care too much about the 20%'s reasons - it's the next 30%'s reasons for their positions, that matter a great deal more.Rationalists working together might be able to achieve something of note in influencing politics on an issue if it's merely unpopular to the tune of 4:1.

Opinions change. Based on evidence, even, sometimes. If the pot states work out, people might be willing to give it a chance. But it won't happen if its working out is not pointed out.

Second, there's a big difference between ending the war on drugs and legalizing everything. Simply reducing drug possession or use-without-a-vehicle-involved crimes to misdemeanors would be an enormous step in the right direction and would be way more palatable to the masses than wiping out the laws altogether.