Washington — Galvanized by the lightning-in-a-bottle success of conservative "tea party" candidates, moderate Republicans and others in the political center are looking for ways to push back against what they see as an advancing tide of ideological extremism. "Middle America is being ignored by Washington and the media. Centrists are desperate for a voice today; they feel entirely unrepresented," said Mark McKinnon, a political strategist and former advisor to President George W. Bush. "The tea party has tapped into voter frustration and anger," he said, "but does not represent millions of Americans in the vast middle." The moves reflect political...