The science on medical marijuana use is in: http://students.washington.edu/sunila/JOM_5-3-03.pdf
The results? A few quotes from the article:
In its 4,000+ years of documented use, there is no report of death from overdose with cannabis. In contrast, as little as 2 grams of dried opium poppy sap can be a lethal dose in humans as a result of severe respiratory depression. This fact about opium is borne out today in the unintentional deaths from prescribed opioids that continue to escalate.
It is clear that, as an analgesic, cannabis is extremely safe with minimal toxicity. Unlike opioids, cannabinoid medicines do not promote appetite loss, wasting, and constipation, but instead can be used therapeutically to treat these symptoms.
Nonetheless, the purpose of this article is not to discuss the pros and cons of medicinal versus recreational marijuana use. That is a totally separate and altogether different issue. Yet, at the very least, it should be noted that there is no evidence that recreational cannabis use is any higher in states that allow for its medicinal use.
The article drew data from over 33 controlled clinical trials taken over 38 years. It is irrefutable and makes plain that Marijuana has no business being a Schedule I drug.
Republicans should take the point on this from a policy perspective. Become known as the party who fought to end an illogical and harmful policy and as the party that aligns itself with the truth. Speak on it every chance you get. Arm yourselves with the information and decry those who argue from any basis of fear, rhetoric, or anecdotes. If you find yourself running low on material, review "The War on Drugs is Lost" at National Review.
Take this issue and make hay with the people you represent, and the ones you hope to represent. Or simply let the Democrats have it by default. Drug policy reform is inevitable; for now, your legacy is yours to define.