For people who still don’t believe that medical marijuana is a mainstream issue supported by a majority of Americans, last night’s GOP Senate  primary in Kentucky provided just one more example. Newcomer Rand Paul, son of Republican congressman Ron Paul, defeated establishment candidate Trey Grayson, in part, because of his support for medical marijuana laws. Here’s how the L.A. Times described it: “Grayson and his allies sought to portray Paul, a Bowling Green eye doctor, as something of a kook.…