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.
I was thinking about the hazards of bad government, and wondering if there was a way for the LW community to do something to oppose them, and it occurred to me that we might be picking up the problem by the wrong end.
The usual way of thinking about political action is to start with one's political identity (progressive, libertarian, whatever), and that's likely to put one at odds with people who have opposed identities.
Instead, I believe there are projects which could appeal to rationalists across a wide range of the political spectrum. A couple I can think of are opposing the war on drugs and improving judicial systems. Any other suggestions?