Sarah Palin’s book tour is a big story, and I think Ben Smith has the best political take on it so far, but it’s worth pointing out that a huge crowd for a conservative book is not a phenomenon unique to Palin. In March, radio host Mark Levin came to Tysons Corner, in liberal northern Virginia, to sign copies of his book “Liberty and Tyranny.” The massive size of the crowd that turned out in fairly cold weather was a minor story on conservative blogs at the time; “thousands” lined up in a five-hour queue. There’s even video of the event.