A real conservative and a real liberal face off for the party-switcher’s seat. Philadelphia — Both men have taken on their parties. Both hold Harvard degrees. And they seem to like each other, at least personally. But that’s where the similarities end between the two candidates in Pennsylvania’s Senate race, a clash Karl Rove predicts will “be among the country’s hardest fought.” Republican Pat Toomey, 48, a former congressman from the Lehigh Valley, now faces Rep. Joe Sestak (D., Pa.), 58, a former Navy admiral. Sestak’s victory in Tuesday’s Democratic primary, where he toppled Sen. Arlen Specter, a 30-year incumbent,...