WASHINGTON (CNN) — In what the Washington Post is describing as a "stumble," Democratic presidential candidate Joe Biden said in an interview with the paper Wednesday that Washington's high minority population is one of the reasons for the city's education problems. Explaining why schools in Iowa are performing better than those in Washington, D.C., Biden told the Post, "There's less than one percent of the population of Iowa that is African American. There is probably less than four of five percent that are minorities. What is in Washington? So look, it goes back to what you start off with, what...