In another serious blow to the Republican National Committee, one of its top fundraisers — and its few remaining connections to the traditional GOP donor base — has resigned a senior, unpaid position. Former Ambassador Sam Fox, a top supporter of George W. Bush who was one of the co-chairmen of the Republican Regents — the RNC's top-level fundraising board — has left the post, two Republican sources said. Fox, a Missouri businessman who was Bush's ambassador to Belgium, was one of the RNC's few remaining connections to the deep-pocketed Republican establishment and was viewed as the heaviest hitter among...