AUGUSTA, Ga. — Georgia's governor is pushing clinical trials for a marijuana-derived drug that proponents say could help treat severe seizure disorders among children, an unlikely election-year move for a Republican in a conservative part of the country that is just beginning to warm up to medical marijuana in narrow circumstances. Since 1996, 23 states around the country and the District of Columbia have legalized comprehensive access to medical marijuana, and two have decriminalized the drug entirely. But the South has largely resisted out of fears it could lead to widespread drug abuse and other social ills.