Barack Obama's campaign has come up with a humorous comeback to Joe the plumber. At every campaign stop, Republican rival John McCain mentions Joe Wurzelbacher, who complained to Obama that his tax cut proposal would penalize small businesses. In a new video today, Al the shoe salesman computes the tax cut he would get under the two candidates, using the Obama camp's trusty tax calculator. Al is Al Bundy (played by actor Ed O'Neill), the aggrieved husband in the comedy hit "Married with Children," which aired during the late 1980s and 1990s. Al makes $20,000 a year and has kids....