A Washington Post/ABC News poll released Wednesday morning found that Americans are divided on tax plans proposed by two of the leading contenders for the Republican presidential nomination, businessman Herman Cain and Texas Gov. Rick Perry. The poll found that a majority of Republican voters favor the flat tax but a majority oppose Cain’s plan. The poll found only 36 percent of the total population surveyed favoring Cain’s “9-9-9 plan.” The plan, which has become one of the cornerstones of Cain’s campaign, would establish the federal income tax and the corporate tax rate at 9 percent while adding a national...