By Ben Blanchard and Benjamin Kang Lim
BEIJING (Reuters) - Three years ago, the mayor of China's sprawling southwestern city of Chongqing was asked to describe how well he got along with his then boss, the ambitious Communist Party leader Bo Xilai.
"Like fish and water," the portly Huang Qifan told reporters on the sidelines of the annual full session of parliament, using a Chinese expression meaning an almost symbiotic relationship. "Everything is great, magnificent. The whole Communist Party secretariat works smoothly together with one mind."
Bo was dramatically ousted from his post last year following lurid accusations of corruption and murder.
Huang, still Chongqing mayor, said this year that Bo's legacy had been "banished", and the "vanity projects" he championed which "tired the people and drained money" would never be allowed to happen again.
As Bo goes on trial this week, Huang's survival in office is a signal of China's hesitation in fully taking its customary hard line against senior party members who fall from grace.
Several junior officials lost their jobs or were detained because of their proximity to Bo, but Huang is one of two senior allies not purged, underlining the leadership's caution as new President Xi Jinping seeks to maintain stability and unity.
Bo was an advocate of populist, leftist welfare policies and his downfall exposed ideological schisms in the party and society at large which still exist.
Xi needs unstinting support at a party plenum later this year to endorse an ambitious program to rebalance the world's second-largest economy and will be keen to put the Bo scandal behind him with a minimum of fuss.
Huang's survival, which has come against all the odds, was ensured once he had disavowed his former mentor.
The mayor was once seen as the brains behind Bo's grandiose economic plans for foggy Chongqing, which included an ambitious urban renewal scheme and an egalitarian narrowing of the stark rural-urban income gap.
He was Bo's right-hand man, even as the party chieftain's rule began to crumble when his police chief Wang Lijun sought political asylum at the U.S. consulate in nearby Chengdu city in February last year.
Huang led security personnel to besiege the U.S. mission, according to sources with ties to the leadership or with direct knowledge of the case.
Wang had fled there after confronting Bo with information that his glamorous lawyer wife, Gu Kailai, had murdered the couple's friend, British businessman Neil Heywood, setting off the scandal which eventually bought Bo down.
Wang hid in the consulate for more than 24 hours until officials from Beijing coaxed him out and put him on a flight to the capital, where he divulged details of the murder safely away from Bo.
Both Wang and Gu were jailed last year.
After Bo's downfall, Huang redeemed himself by writing a self-criticism - a throwback to the Mao-era practice of self-denunciations for political or ideological mistakes - and selling out Bo, the sources said.
"He exposed Bo Xilai's ambitions," a source with leadership ties said, referring to Bo's barely concealed public campaign for a seat on the Communist Party's powerful inner circle, the Politburo Standing Committee.
"Huang Qifan also exposed wiretapping by Wang Lijun," the source said, referring to the bugging of telephone calls between then-President Hu Jintao and a central government anti-corruption investigator who was in Chongqing.
"Politically, he (Huang) is someone who can't be knocked down," the source said. "But he stayed on also to stabilize Chongqing."
The sources declined to elaborate.
"Once Bo Xilai went down, people defected, and I think Huang Qifan is a very good example of that," said Bo Zhiyue, an expert on elite Chinese politics at the National University of Singapore, who is not related to Bo Xilai.
"As long as you distance yourself from this person, you criticize them, you offer evidence or whatever, you cooperate with the authorities, you will be ok," he added.
A number of Bo's most prominent cronies and supporters have however been either sacked or detained, including Xia Zeliang, party secretary of Chongqing's Nanan district, and Xu Ming, a plastics-to-property billionaire entrepreneur whose long association with Bo extended for over two decades.
However, another senior Bo ally who has so far survived is Zhou Yongkang, once China's powerful domestic security tsar.
Zhou was implicated in rumors last year that he hesitated in supporting the party's move against Bo. However, his reputation was also dented when security forces failed to prevent blind dissident Chen Guangcheng from fleeing to the U.S. embassy in Beijing from house arrest in a nearby province last year.
The hulking, grim-faced 70-year-old Zhou stepped down along with most members of the Standing Committee at the 18th party congress last November.
His replacement failed to get a position on the new Standing Committee and was only given membership of the larger Politburo, which showed party concerns the domestic security position had become too powerful and also that Zhou was out of favor.
Speculation continues to surround Zhou, fueled earlier this month by a story from U.S.-based Chinese news site Duowei, which said he was being investigated for graft. However, the report was later withdrawn and the government has not commented.
Three of Zhou's allies are currently under investigation, including the deputy party boss of Sichuan province, Li Chuncheng, who had for many years overseen development of the province's prosperous capital, Chengdu.
However, sources with ties to the leadership, as well as analysts, are skeptical Zhou will be taken into custody because of an unwritten rule that incumbent and retired members of the Standing Committee are immune from prosecution.
"The norm has been to avoid attacking (incumbent) and former Standing Committee members, for if they do so it opens a Pandora's box," said the University of Singapore's Bo.
(Additional reporting by John Ruwitch in SHANGHAI; Editing by Raju Gopalakrishnan)