But Mr. Bo was also adaptable. As mayor of Dalian in the 1990s, he sought to remake the northeastern coastal megalopolis into a new Singapore. To waves of favorable publicity, his government rewarded citizens who reported rude taxi drivers and fined those who uttered unpleasantries like “nao you bing,” or, roughly, “numbskull.”

In Dalian, and in Chongqing, he could pursue liberal causes as easily as leftist ones. He proposed experimenting with direct elections in local townships, courted foreign investment, mounted aggressive tree-planting and pollution cleanup campaigns and built low-income housing.

Only Prime Minister Wen Jiabao, who has cultivated an image as the caring grandfather figure of the national leadership, rivaled Mr. Bo’s popularity. But while the modest Mr. Wen was always careful to show his loyalty to the party’s central command, Mr. Bo often seemed to appeal to the disenfranchised masses who longed for someone to shake things up.

“Bo Xilai was differentiating himself from other leaders in a very conspicuous way,” Susan Shirk, a scholar of the Chinese elite at the University of California at San Diego, said in a recent interview. “His style of politicking was antithetical and threatening to a political oligarchy that was trying to keep the competition among themselves hidden from the general public.”

Mr. Bo’s ambition and abrasive style made some enemies in the elite, notably Mr. Wen. His posting in 2007 to Chongqing, deep in China’s interior, was seen by some as an effort to sideline him. Instead, it became the base for his campaign to join the Politburo’s Standing Committee, the nine-member body at the peak of the Communist hierarchy whose membership will turn over this fall.

In a governing elite that makes big choices by consensus, experts say, Mr. Bo might well have vaulted onto the Standing Committee with the support of sympathizers, had Chongqing’s police chief, Wang Lijun, not fled to the American Consulate in Chengdu, in nearby Sichuan Province.

Mr. Wang carried papers that he said implicated Mr. Bo’s family in a criminal inquiry of the death of a British businessman, Neil Heywood, an acquaintance of the Bo family. Mr. Bo and Mr. Wang are now said to be confined in Beijing while party officials investigate those and other claims.