Inevitably, the Democratic Party fest in Charlotte, N.C., will be compared to last week’s Republican gathering in Tampa, Fla. The speeches by the vice president and president will be contrasted with those of Republican nominees Paul Ryan and Mitt Romney. The Republican convention was marked by patriotic rhetoric, Horatio Alger tales of upward mobility and a diverse lineup of speakers presenting to the overwhelmingly white, older and affluent delegates. Democrats are not lacking for patriotic salutes, uplifting tales and diverse speakers. They are addressing a crowd that is younger and more diverse than the Republican crowd. But the starkest contrast …