In spite of remarks by the Foreign Ministry to the effect that the Zhao missive, entitled "Letter to the Politburo and the Preparatory Committee for the 15th Party Congress", was a fabrication of the overseas media, the General Office of the Central Committee took it seriously enough to send a circular to attempt to contain the damage.
According to Chinese sources, the document, which was recently relayed to mid-ranking cadres and up, warned of dangerous elements spreading a "so-called Zhao Ziyang letter" and other rumours against the Jiang leadership.
The circular particularly asked cadres not to give credence to two "falsehoods" in the missive: that the CCP made a mistake in its handling of the June 1989 events, and that it was contrary to the teachings of Deng Xiaoping, Mao and Lenin to vest major powers in a "core figure" in the party.
The Central Committee document further urged officials of all levels to "rally more tightly around the leadership with Mr Jiang as its core".
It is, of course, understandable why the Jiang faction should have moved quickly to disinfect what some of the President's affiliates call the "Zhao poison".
Having been printed in two Hong Kong papers last week, the four-page "Zhao manifesto" will have been seen by thousands of cadres with the rank of bureau chief or above. Regardless of whether it was Mr Zhao - or a Zhao sympathiser - who penned the piece, it reflects the thinking of the party's liberal wing.
The petition stated, for example, that the suppression of the student demonstrations had been against "the principles of the revolutionary humanitarianism of Marxism".
Yet what Mr Jiang and his advisers found most offensive was the challenge to the President's "core status". The Zhao missive cited the little-known but authentic "Regulations on Political Life in the Party" of 1980, which were drafted under Deng's directions.
The regulations said the party must be run by a collective leadership; and they warned against the dangers of "the authoritarianism of one-person [rule]". Two years later in 1982, the position of party chairman was abolished as evidence of Deng's opposition to the personality cult.
The Zhao petition also quoted Deng's 1980 dictum on building institutions and systems to combat the rule of personality. The climax of the Zhao letter was a request that the party abolish the practice of ascribing the "core status" to a single person. It quoted Mao to the effect that only a collective leadership, not an individual politician, could be called a "core".
What some diplomats regarded as "Zhao's last offensive" could not have come at a worse time for Mr Jiang as he was taking measures to consolidate his grip.
Since Deng's death last month, he has spearheaded a national campaign obliging all cadres publicly to salute his supremacy.
Mr Jiang is also canvassing support for his attempt to revive the party chairmanship - and to assume that position at the 15th Party Congress later this year.
Leaders of the party's moderate faction, such as National People's Congress Chairman Qiao Shi and Chinese People's Political Consultative Conference Chairman Li Ruihuan , have repeatedly vowed to revive political-reform ideals laid down by Deng in 1980.
In recent interviews with the foreign and domestic media, Mr Qiao particularly highlighted Deng's dictum about putting institutions and systems before the rule of personality. In internal discussions, members of the party's liberal and moderate wings have also been taking a second look at a speech Mr Zhao delivered to the now-defunct Research Office for Political Reform in 1987.
Then, the former party boss pointed out the key to building up "inner-party democracy" was to ensure a healthy working relationship between the politburo standing committee, the politburo, the central committee and the central committee secretariat.
A major reason why Mr Jiang wants to become party chairman, however, is his hope that the chairmanship would bestow on him Mao-style authority to ride roughshod over the politburo and other top organs.
Political analysts said that, at a time when the leadership was preoccupied with preparations for the 15th Congress, the central message of the Zhao letter - that the party "makes a pledge to the entire people that it has the determination and the means to gradually implement the reform of the political structure" - had struck a chord of resonance.
Ironically, the analysts said, Mr Jiang had made a commitment to political reform immediately after Deng's death in order to stake a claim as the true disciple of the Chief Architect of Reform.
Take for example, this now-famous one-sentence reference to political reform in the President's eulogy at Deng's funeral: "We must insist on deepening the reform of the political system and other systems".
The President's public-relations consultants have told Hong Kong and foreign journalists that he meant what he said. "Mao's greatest contribution was founding the People's Republic of China," they added. "Deng is remembered for his economic reform. And Jiang will make his mark in political reform."
As well, Mr Jiang's neo-conservative allies have told visiting foreign delegations that the "next major step" for China would be political reform.
According to sources close to the Jiang camp, however, what the President had in mind was relatively unexciting initiatives such as "boosting consultation with the democratic parties" and "separation of government and enterprise".
The sources said Mr Jiang had reinforced steps to contain the "Zhao challenge" by, for example, keeping close tabs on the activities of both the former party chief and allies like former president Yang Shangkun .
Yet, unless Mr Jiang could demonstrate a willingness and ability to pick up on the reforms outlined by Deng in 1980, the moral high ground would inevitably be hogged by a 77-year-old man who was declared a quasi-traitor for sympathising with the Tiananmen demonstrators.