The Associated Press is reporting that General David Petraeus will be leaving Iraq to become the next commander of U.S. Central Command. According to AP, Lt. gen. Ray Odierno will be taking Petraeus' position as the senior commander in Iraq. We speak with Demetri Sevastopulo of the Financial Times.

Slavery is not legal anymore, but there may be more slaves today than at any point in history. We speak with John R. Miller, who served as director of the Bush administration's Office to Monitor and Combat Trafficking in Persons.

Exit polls in yesterday's Pennsylvania primary show that both Hillary Clinton and Barack Obama were hurt by recent negative campaigning. We speak with The Wall Street Journal's Gerald Seib, who argues that the long, hard race is good for both candidates.

The Democratic nomination is likely to be decided by superdelegates, many of whom remain undecided. We speak with one, cattle rancher and Montana State Democratic Party Chairman Dennis McDonald, who says he won't announce who he's supporting until his state votes on June 3.

Journalist Calvin Trillin writes about the rickshaws in the April issue of National Geographic and joins us to talk about this debate.