I was firmly conservative long before I first heard Rush, sometime in 1988. But I would credit Rush for changing many minds for conservatism, in fact, he has probably single handedly done more to advance the conservative perspective than nearly anyone in contemporaty history.
I think Rush’s great talint is that he confirms to you what you already know. I don’t know how many he has brought over, but I am certain he has kept many on our side, and kept the MSMers from peeling them away.