President Barack Obama’s got a volunteer army — and all their marching orders come from carefully organized paid generals back at headquarters. Obama won two terms by harnessing a grassroots movement through a tightly controlled, top-down campaign organization. Now the group formed out of Organizing for America is now bringing that approach to Organizing for Action. It’s what differentiates OFA from other grassroots groups, and even the Democratic National Committee: they’re combining large-dollar donations and unpaid local leaders for a carefully built, lasting structure that they believe will be just as effective in supporting the president as it was in...