BEIJING — In a sign that China’s political season is heating up, reports circulated widely on Wednesday that one of the country’s most famous crime fighters had tried to defect to the United States.

The reports were impossible to confirm, but China’s social media were filled with speculation about the fate of Wang Lijun, a onetime rising star in the western megacity of Chongqing, where he had been the deputy mayor overseeing public security.

Mr. Wang, 52, shot to national attention as a one-man gangbuster, taking on Chongqing’s notorious organized crime syndicates in the city of 29 million. Last year he successfully tried and had executed the city’s most powerful mob boss, and he hired local writers to produce an official history of the campaign. He boasted that he would hire a prominent Hong Kong director to make a movie of his exploits, saying it would be modeled on “The Godfather.” Mr. Wang had been hired by the city’s Communist Party secretary, Bo Xilai. His success helped propel Mr. Bo onto the short list for the powerful Standing Committee of the Communist Party’s Politburo.

The party is scheduled to meet this year for a once-in-a-decade changing of the top guard. Mr. Bo is already on the 25-member Politburo and has made no secret of his ambition to take the next step to the Standing Committee, which has 9 members.