Yet, for all its importance, democratic development is not high on the agendas of either Tang or Leung. In a speech outlining his election manifesto on December 19, Tang said he wanted to ensure that the chief executive election in 2017 would be conducted in a 'fair, open and just manner', without giving details.

Tang, who is seen as the preferred candidate of Beijing and the business community, said during a forum on December 28 that there should be a reasonable nomination mechanism for the chief executive election in 2017 to ensure the race was conducted in a serious manner.

According to a decision taken by the National People's Congress Standing Committee in December 2007, universal suffrage will be allowed for the election of the chief executive in 2017 and the Legco thereafter. But details of the 2017 and 2020 polls have yet to be settled.

Under the Basic Law, a 'broadly representative' nominating committee will put forward chief executive candidates for a popular vote in accordance with 'democratic procedures' when universal suffrage is in place.

However, pan-democrats have warned of a 'fake universal suffrage' as there is a dearth of details about the arrangements for attaining a 'one man, one vote' system by 2017 and 2020. Fearing their candidates might be screened out in a chief executive race, they are seeking an assurance that the procedures will not be even more stringent than at present.

For this year's chief executive election, any candidate who secures 150 nominations from the 1,200 Election Committee members is eligible to stand for the committee's poll on March 25.

Speaking at a forum on December 28, Tang said: 'Currently, a person has to secure one-eighth of the total number of Election Committee [members' votes] to qualify as a chief executive candidate.

'For the 2017 chief executive election, it's fine to reduce the proportion to one-tenth, one-twelfth, or even fewer. But we need to discuss this later and forge a consensus within the community.'

When pressed on Tuesday about the requirements for qualifying as a chief executive candidate when universal suffrage is in place, Tang said the nomination process should be conducted in the 'most open' manner so that all candidates who were interested in the race would be able to take part.

Asked whether a candidate from the pan-democratic camp would be prevented from entering the race in 2017, he said he did not envisage such a scenario.

Leung, the former Executive Council convenor, was equally coy about how to attain universal suffrage when he declared his candidacy for the top job.

In his declaration speech delivered at the end of November, Leung said: 'We shall conduct the process of democratisation according to the provisions of the Basic Law and pertinent NPC resolutions.'

Both Tang and Leung have also refrained from making any pledge on the steps needed to abolish functional constituencies by 2020.

Tang said last month that the present method of electing the trade-based seats was incompatible with the principles of equal and universal suffrage, adding that functional constituencies had a 'historical background'.

In an interview with the South China Morning Post in the middle of last month, Leung, who is enjoying a substantial lead over Tang in popularity ratings, said that if he became chief executive, shortly after taking up office he would launch a public consultation on the arrangements for attaining universal suffrage for the chief executive election in 2017 and the Legislative Council in 2020.

Following a new inquiry from the Post this week Leung was more forthcoming about the details for electing the chief executive by universal suffrage in 2017.

'I believe the composition of the nominating committee should be as broad as possible,' he said. 'Compared with the current Election Committee, I can see some room for improvement as far as the formation of the nominating committee is concerned. The broad principle is to increase its democratic elements and representativeness. I would also like to see a relatively lenient threshold for nomination.

'In general, I expect and believe that the nominating committee and the nominating procedures in 2017 will show no retrogression compared with current arrangements.'

In the pan-democratic camp, Democratic Party chairman Albert Ho Chun-yan is competing with Frederick Fung Kin-kee, a lawmaker for the Association for Democracy and People's Livelihood, in a primary election on Sunday to choose the bloc's candidate for chief executive.

Both Ho and Fung suggest that the nomination threshold for candidates in the 2017 chief executive election should be as loose as possible as to allow more candidates to contest the top job.

Dr Chan Kin-man, an associate professor with the Chinese University's department of sociology, said both Tang and Leung failed to show firm commitment to implementing universal suffrage if either became chief executive.

'But as a candidate who is struggling to secure the required nominations from the Election Committee to enter the chief executive race, Leung should be well aware of the negative impact of a stringent nomination threshold and he should put forward more progressive proposals,' Chan said.

Leung and his allies suffered setbacks in last month's voting for sub-sector representatives on the 1,200-strong Election Committee. Leung's known supporters won 50 seats, compared with 203 for Tang.

Chan, a core member of the Alliance for Universal Suffrage which two years ago negotiated with the central and Hong Kong governments on the political reform package for this year's elections, said contenders for the top job should spell out their ideas on what steps they would take to achieve universal suffrage.

'They should also emphasise that no candidates should be screened out of the race because of their political aspirations,' Chan said.

The alliance proposed that a 1,200-strong Election Committee nominate candidates for the chief executive in 2017, with any candidate who obtained 100 nominations being eligible to run for election.

Dr Ma Ngok, a political scientist at Chinese University, said Leung - who is seen as the underdog in the chief executive race - was more inclined to adopt a more aggressive approach on the topic of universal suffrage to win support from members of the public.

Ma said, based on his previous contact with Tang, the former chief secretary lacked the passion to strive for eventual attainment of universal suffrage.

'But Leung would have the political will to resolve the question of universal suffrage if he believes there is a need to do so and would gain from the process,' Ma said.

Chan said both Tang and Leung lacked the imagination to resolve the deadlock over universal suffrage.

'When Donald Tsang Yam-kuen stood for re-election as chief executive in 2007, he promised to resolve the question of universal suffrage 'once and for all',' Chan said.