During a closed-door gathering of major donors in Southern California on Monday, the political operation spearheaded by the Koch brothers unveiled a significant new weapon in its rapidly expanding arsenal — a super PAC called Freedom Partners Action Fund. The new group aims to spend more than $15 million in the 2014 midterm campaigns — part of a much larger spending effort expected to total $290 million, sources told POLITICO., The vast network of political nonprofit groups they helped build has mostly funneled its unprecedented political spending into issue-based campaigns that usually slam Democrats for supporting big government but seldom...