Ames, Iowa — Political organizer Peter Singleton tells National Review Online that Sarah Palin will likely launch a presidential campaign by the end of September. “I believe that she will run,” he says. “I can’t see her sitting this election out.” Palin, a former Alaska governor, is scheduled to address a tea-party rally on September 3 in south-central Iowa. Singleton is one of the forces behind the event, working with grassroots groups. “Labor Day will kick off the Republican campaign for the nomination,” he hints. “She is going to make a major, major speech.” [....] GOP presidential contenders, from Rick...