In one of the most serious political corruption cases in recent history, federal prosecutors have accused a senior U.S. senator of trading the power of his position for cash, gifts and gold. Tracey Tully, who covers New Jersey for The Times, tells the story behind the charges against the senator, Robert Menendez, and his wife, Nadine, and describes the role played by Wael Hana, an Egyptian American businessman at the center of the allegations. Guest: Tracey Tully covers New Jersey for The New York Times.