A new doping scandal is rocking the world of competitive swimming, as the Paris Olympics approach. These allegations are raising questions about fairness in the sport and whether the results at the summer games can be trusted.Michael S. Schmidt, one of the reporters who broke the story, explains the controversy and what it reveals about the struggle to police doping in sports.Guest: Michael S. Schmidt, an investigative reporter for The New York Times.Background reading: 

• Chinese swimmers twice tested positive for drugs. They kept on swimming.
• U.S. swimming stars assailed the World Anti-Doping Agency ahead of the Olympics.

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