Former Alaska governor Sarah Palin though derided on the left and recently dismissed by former vice president Dick Cheney as a poor pick in 2008 is nevertheless proving her enduring power within the Republican Party in the most concrete of ways: She keeps picking winners. Each of five candidates she has endorsed this year who have faced primaries or other campaigns have won, including former Texas solicitor general Ted Cruz, who Tuesday beat the states well-connected lieutenant governor for the Republican nomination for the U.S. Senate. In Palins biggest test yet as a kingmaker, she heads Friday to...