As the Republicans have never had the pothead vote, its kinda moot.
I think you would be stunned at how many conservatives smoke pot. In fact huge numbers of small business owners became that because they could not pass drug testing at corporations or gov jobs. In fact if the Republicans grabbed this issue and ran with it they could cut off the Dems balls at the root. Besides about 50% of the crime in this country is pot related, think about it for a moment.