When Annabel Park imagined what it would be like to head a new national political movement, here is what she had in mind: a coming together of engaged, intelligent citizens who had tired of the angry rhetoric and accusations of the Tea Partiers; Americans of all political persuasions joining in a spirit of equanimity to discuss the nation's problems, and maybe even share a laugh. It was this beautiful vision that danced in Park's head on a recent Saturday as she made her way to Busboys and Poets, a cafe in Washington, D.C., for one of nearly 500 Coffee Party...