A new poll shows Wisconsin Gov. Scott Walker sitting atop a handful of 2016 GOP contenders in the early presidential state of Iowa, notching a 10-point lead over his nearest rival. Mr. Walker, who has not yet officially declared his candidacy, was the choice of 23 percent of Republicans, followed by Sen. Marco Rubio of Florida at 13 percent and former Florida Gov. Jeb Bush at 12 percent, according to the survey released Tuesday by the Democratic firm Public Policy Polling......................"