Mr Wen's four-day visit to Sichuan's worst-hit areas just hours after the quake afforded images of a moderate communist leader similar to those of his elected counterparts in free democracies. It was a sight never before seen on the mainland.

'These two pictures, standing in stark contrast, demonstrate how much China has changed and how much its leadership has changed since the Tiananmen crackdown,' said Zhu Xing-qing, a veteran journalist who was editor of the World Economic Herald, the ground-breaking newspaper closed by authorities in May 1989 for pushing political and economic reform on the mainland.

The collective memory of June 4, when People's Liberation Army soldiers opened fire on pro-democracy students and their supporters, is one of political oppression at home and pools of blood abroad. Since that night, scrutiny of China's human rights record has become a major focus in relations with the west.

While many believe the generation that has come of age in the past two decades dismisses Tiananmen and its legacy, some liberal intellectuals point to the incident as a watershed of contemporary Chinese thought, history and politics.

'While the event itself did not change China's political system, it did lay the theoretical foundation for later changes. It became the starting point for a fundamental change in its political system,' said Xu Youyu , a liberal philosopher at the Chinese Academy of Social Sciences.

In his recent paper to mark the 20th anniversary, titled: 'China's Evolution of Thought in the Past 20 Years - 1989 to 2009', Professor Xu summarised the legacy of the June 4 crackdown as the point when the party lost its legitimacy to govern; when the people shifted their aspirations for political advancement from focusing on democracy to seeking protection of human rights and a constitutional government; and when the nation realised that violent revolution must be abandoned in favour of rational, non-violent evolution.

Professor Xu said the decision to resolve the issue with a massacre ruined the party's legitimacy, given its links to student movements throughout the 20th century.

Peking University students' march to Tiananmen in 1919, calling for science and democracy, was said to be the moment the party was conceived, though it was actually born two years later. That May Fourth Movement and all the ones that followed were the wellsprings of the protests in 1989.

The government has always paid lip-service to those events, though it now emphasises the patriotic aspects of the May Fourth Movement while ignoring the fact that the students' principal demands were for democracy and civil liberties.

Professor Xu said calls to protect human rights and maintain a constitutional government now prevail in political activism outside the party. They cite Charter 08, a manifesto published last year and signed by about 300 political activists, academics, writers and lawyers. Hailed as the most significant act of public dissent against the ruling party since 1989, it calls for the protection of human rights, an end to monopoly rule and a new, democratic constitution.

Steve Tsang, a professor of politics at Oxford University, put forward the concept of 'consultative Leninism' - which he defined as 'a system that blends together the Leninist disposition to, and instrument of, control with innovations from other sources' - as the legacy of 1989.

'The June 4 legacy is simply that the Communist Party, taking the form of consultative Leninism, works hard to rewrite the history of 1989 to help consolidate its political power and enhance China's development,' he said.

'The party believes it has picked the right path since 1989, and this new path is working well both for the party itself and for China. It is a robust and resilient system for the foreseeable future.'

Many agree the improvement of governance and its ruling philosophy have helped consolidate the party's grip on power.

'China has changed dramatically, and so has the leadership's image at home and abroad. The leadership has undertaken a painstaking campaign to rebuild its popular support over the past two decades,' veteran journalist Zhu said.

As communist philosophy had been unable to sustain the Chinese people since Tiananmen, Professor Tsang said, the ruling party had tapped other sources to boost its legitimacy, including nationalism, national economic self-interest and a deep Chinese aversion to social or political chaos. 'The defining feature of consultative Leninism is the promotion of nationalism as the new ideological force that binds the country together under the leadership of the party,' he said.

The government has banned any public calls for western-style democracy and civil liberties, but has endorsed or supported numerous student demonstrations against the west in recent years.

Professor Tsang said the choice of nationalism as the new, though informal, state ideology was meant to enhance the party's capacity to stay in power in two mutually reinforcing ways. 'It is to provide a new ideological basis for legitimacy on one hand and to serve as a new rallying force to develop a national aspiration around the leadership of the party on the other.'

While the party leadership had refused to undergo any substantive political reform, it had moved gradually to improve governance, encourage people to better themselves economically, allowed greater personal freedom and expanded political participation.

The 'united front' was expanded to recruit businessmen into the party under former party chief Jiang Zemin's 'Three Represents' theory. President Hu Jintao has introduced 'people oriented' and 'social harmony' to serve the people's interests. Analysts said the swift and largely effective response to the Sichuan quake last year showed how much governance had improved.

'Today's leaders have learned how to seize any event at any moment to control, shape and direct public opinion,' Zhu said, citing the effectiveness of television images of 'Grandpa Wen' in Sichuan as an example.

Despite the changes since 1989, the party remains wedded to the doctrine that a modern economy can operate without political liberalisation. Yet a rising number of intellectuals disagree, arguing that the spirit of the 1989 movement is still alive.

Although the first anniversary of the Sichuan quake has passed, the communist leadership is likely to feel strong tremors during next Thursday's politically sensitive 20th anniversary of the Tiananmen Square bloodletting.