Conservative talk-radio host Mark Levin is defending himself against charges that he engaged in a quid-pro-quo transaction with the Senate Conservatives Fund, promoting the right-wing group after it spent hundreds of thousands of dollars on his book. Since Sept. 10, SCF has spent $427,000 on copies of Levin's "Liberty and Tyranny," according to Federal Election Committee filings. Those books were given to donors who provided $25 or more to the group. In that time, Levin has frequently promoted the SCF on his show and on his Facebook page. "Senate Conservatives Fund is dedicated to electing true conservatives to the Senate!"...