ON MAY 23rd four people went to a police station in Beijing with a petition demanding justice. Victims of official wrongdoing often make such trips, and usually they are given short shrift. But this was no ordinary group of the downtrodden. The petition bore the names of nearly 10,000 people accusing a liberal intellectual of slandering Mao Zedong and attempting to overthrow the Communist Party itself. Emboldened by a chill political wind, diehard Maoists in China are rising to confront their critics.

The Maoists' appeal for the arrest of Mao Yushi, a well-known economist (and no relation of the late chairman), is their most concerted public attempt in many years to put pressure on the government. A clutch of Maoist websites frequently vilify intellectuals such as Mr Mao. But campaigning openly for someone to be put on trial is unusual. It is a symptom of a recent escalation of ideological struggles between China's West-leaning liberals and conservative hardliners. The Maoists froth at the extreme fringe of the hardline camp. But their cause is gaining headway as the authorities wage an intense crackdown on dissent, putting pressure on NGOs and arresting or otherwise making vanish dozens of government critics.

Mr Mao, who is 82, is the soft-spoken head of a remarkably independent think-tank, the Unirule Institute of Economics. His crime, say the Maoists, was his article on April 26th on a blog hosted by Caixin, an outspoken Chinese news organisation. The article, “Restore Mao Zedong as a Man”, is among the most scathing attacks on the chairman seen in China's mainstream media. It was later removed from Caixin's website and also disappeared from several others that had reposted it. Propaganda apparatchiks clearly wanted it eradicated.

All year the Communist Party has been jittery about the possible spread of Arab-style “jasmine revolution” to China. (The word “jasmine” has been all but banned in the media, as has the flower itself in markets.) Now the party is all the more anxious as it prepares to celebrate, on July 1st, the 90th anniversary of its founding. It does not want the occasion to be clouded by misgivings about the man who led it to power. Mao is too intimately linked with the party's identity to allow any further examination of the “mistakes” the party sheepishly admitted he made, five years after his death in 1976.

Mr Mao's essay said the party's takeover of the country in 1949 did not bring happiness to China: “On the contrary, it plunged [the Chinese] into an abyss of misery for 30 years.” Mr Mao said 50m Chinese died as a result of Mao's policies, “for which he felt not the slightest remorse”. He did not fully account for the figure, but the 30m deaths he attributed to Mao's “Great Leap Forward” in the late 1950s is a mainstream estimate among historians; meanwhile around 2m were slaughtered in various political campaigns. A portrait of “the backstage boss who wrecked the country and ruined the people” was still hanging in Tiananmen Square, Mr Mao noted. (The boss's corpse also lies, unmoved, in the square.) It was time, Mr Mao said, to end all the “idolisation” and “superstition” surrounding Mao and assess him as an ordinary man.

Mr Mao says that people have since telephoned him, threatening to beat him up. Language on the internet is strong. “The whole nation is waiting for the dawn, the dawn of a day when Mao Yu-Shit (sic) and other anti-Mao reactionaries who vilify Mao are annihilated,” one person commented on Utopia, a website which is leading the campaign to get Mr Mao indicted. Utopia accuses Mr Mao of subversion and libel. It says funding given to Unirule by the Ford Foundation, based in New York, is evidence of “collusion” with foreigners in his alleged crimes.

Among those named on the website as supporting the campaign are two of the chairman's relatives: Mao Xiaoqing, his niece, and Liu Siqi, the widow of Mao's eldest son, Mao Anying, who was killed in 1950 fighting in the Korean war. Though no one on the list is highly influential, the speed with which Utopia has collected so many names underscores how much popular support Mao continues to enjoy. In some Chinese taxis, talismans of Mao are displayed for luck.

Utopia claims that the police have promised to take the case seriously. But even in its current chilly mood, the party will probably be cautious. It is already facing a barrage of international criticism over the early April arrest of Ai Weiwei, a dissident artist. Mr Ai has now been accused of tax-related offences, as a convenient way to silence a critic without having a contentious political trial like that of Liu Xiaobo in 2009. Mr Liu's sentence of 11 years in prison for subversion helped him win the Nobel peace prize, to China's fury.

Maoist muscle-flexing, however, is not to be dismissed. The party chief of Chongqing municipality in south-western China, Bo Xilai, has become a darling of the Maoists for his attempts to revive a Mao mini-cult. Chongqing citizens are being enjoined to sing Mao-era songs, and officials to go down to the countryside to live with peasants for a few days each year. Few would have guessed at such tastes in Mr Bo when he served as a provincial chief in north-eastern China and as minister for commerce before taking up his current job. But he is the son of one of Mao's comrades-in-arms, Bo Yibo (though persecuted by Mao, Bo Yibo remained a hardliner). Mr Bo is also is a populist who clearly feels that tapping into popular reverence for Mao will help propel him to greater things. He aims to become one of China's most powerful leaders in a shuffle next year. Some analysts believe he may take over the crucial portfolio for domestic security. By cosying up to Maoists, some reckon, Mr Bo could be unleashing forces that make China even less tolerant of the beleaguered liberal camp.

A relative liberal, Wen Jiabao, the prime minister, in a meeting with a visitor from Hong Kong in April, said two forces were causing difficulties for China's reform efforts. One, Mr Wen said, was “vestiges of feudal society” (party-speak for conservatism). The other, he added, was the “pernicious influence of the Cultural Revolution”. Apologists for that orgy of violence, destruction and persecution in the latter years of Mao's rule abound in China's Maoist circles. Qin Xiao, a former chairman of China Merchants Bank and a prominent moderniser, warned in an interview this month that the “evil habits” of the Cultural Revolution were in danger of resurfacing. At least this time, in contrast to earlier hardline crackdowns, some liberals are fighting back.