New Jersey Democratic insiders believe Newark Mayor Cory Booker poses the strongest threat to Gov. Chris Christie in the 2013 gubernatorial election. In Patch’s inaugural Blue Garden State survey, nearly 200 influential Democrats in the state were asked to weigh in with their thoughts on a potential Booker candidacy. The local leaders surveyed include state senators, mayors, town council members and local party chairs. Of the 16 Democrats who responded to the survey, 68 percent agreed with the statement “Cory Booker would be the strongest Democratic candidate against Gov. Christie.” Some 31 …