Supporters believe to this day that it underpins the party's legitimacy and grounds it in a set of guiding principles
Today, speculation about whether it is poised to finish the job has cast a spotlight on one of the most emotive debates simmering inside the party — how much of Mao can it erase without undermining its authority. The debate is also a proxy for the more tangible battle inside the party over the direction and extent of future reforms.
Recent omissions of the term "Mao Zedong Thought" from some policy statements have piqued speculation that the party might remove it from the party charter when it amends the document at the 18th Party Congress, which starts on Thursday.
To critics, boilerplate references to "Mao Zedong Thought" have been devoid of meaning for years. Mao, after all, thought revolution and communism — not harmony and capitalism. It seems clear which path the party has chosen for China.
Supporters, however, note that "Mao Thought" long ago was expanded to encompass much more than just Mao's individual, and often radical, cogitations. It was, at its essence, a set of arguments that originally justified the pursuit of Marxist revolution in poor, agrarian China.
Supporters believe to this day that it underpins the party's legitimacy and grounds it in a set of guiding principles.
This year's downfall of Bo Xilai, the former leader of the western city of Chongqing who once had prospects for higher office, is a consequence of the battle within the party, experts say.
After his appointment in 2007, Bo turned Chongqing into a showcase of pro-Mao "red" culture and his policies for egalitarian, state-led growth. Bo's wife has been convicted of murder and he has been expelled from the party, accused of corruption and abuse of power — charges frequently used to discredit disgraced officials.
"It's not a question of whether they think about it or not," a source with ties to the leadership said of removing "Mao Zedong Thought" from the party constitution.
"It's a question of whether or not they have the guts."
The party's policymaking Central Committee approved an amendment to the party's constitution on Monday that would update the document "to reflect the party's latest theoretical achievements in localising Marxism and practical experience", the Xinhua news agency reported.
Details were not made public.
The new leaders expected to be anointed at the 18th Party Congress, however, have given few hints that they will espouse radical change. Incoming President Xi Jinping and the presumed Premier, Li Keqiang, are seen at best as cautious reformers. However, sources have said Xi and outgoing President Hu Jintao successor are pushing the party to adopt a more democratic process for choosing the new leadership this month, which would be a major reform.
The party has been inching away from Mao since 1981 when it issued a pivotal historical resolution admitting that the revolutionary leader, who had been treated like a god during the 1966-76 Cultural Revolution, had made some large mistakes.
"The horizons of the re-evaluation have continually been pushed back," said Rebecca Karl, a New York University history professor who has written a book on Mao.
By the 1990s, Mao's errors were understood to include not just the Cultural Revolution, but also the 1958-61 Great Leap Forward, which caused a famine that killed as many as 30 million people. The line was later pushed back to include collectivisation in the early 1950s, Karl said.
At the same time, party congresses have been used to formalise incremental policy steps away from much of what Mao stood and fought for, analysts say.
The concept of "Socialism With Chinese Characteristics" was added to the party constitution in 1992 and "Deng Xiaoping Theory" made its way in five years later, formalising China's turn toward the market.
In 2002, the charter was amended to allow entrepreneurs into the party and assert that the party represents the interests of all Chinese people, not just workers and peasants.
Meanwhile, "Mao Zedong Thought", which originated in the 1930s, continues rhetorically to be recognised as one of the party's guiding principles, an extension of Marxism-Leninism tweaked for China.
The term was introduced into the party charter first in the 1940s but was removed in the late 1950s after de-Stalinisation started in the Soviet Union, dismantling the dictator's cult status. The term was re-installed in the late 1960s and has been a part of the constitution since.
"Mao Thought" has been bent and re-shaped time and again over the decades to serve the politics of the day. In practical terms "it has been completely gutted", said Karl.
That does not make it meaningless, though.
"The erasure of 'Mao Zedong Thought' with the continued presence of the party erase the guarantee — however notional, however rhetorical, however far-fetched — of the arrival of socialism somewhere down the road," she said.
Han Deqiang, a Beijing University of Aeronautics and Astronautics professor and founder of the neo-Maoist organisation Utopia, says removal of Mao thought would also pull the rug out from under the party.
"If you take out 'Mao Zedong Thought', then the regime not only has no electoral legality, but would also have no historical legality. Where will its legitimacy come from?" he said.
Mao, the man, remains a potent symbol. His Mona Lisa smile hangs over Tiananmen Square and on banknotes.
Keeping Mao without retaining an element of "Mao Zedong Thought" in the ruling ideology would require some fancy rhetorical footwork and, potentially, some honest discussions party leaders may not be ready for, including about the Great Leap and the Cultural Revolution — politically sensitive topics that are rarely discussed publicly.
"If they are unable to truthfully face up to what happened at that time then they are definitely still going to be bound by Mao Zedong Thought, and will not be able to let it go," said Zhang Sizhi, a lawyer who defended Mao's wife Jiang Qing in her 1980 trial as a member of the "Gang of Four".
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