Dr Raymond Ho Chung-tai, the engineering-sector lawmaker and a National People's Congress deputy, said he had nominated Tang before the scandal over his illegal basement erupted. He added that his nomination would not guarantee he would vote for Tang in the end.

If no candidate gets at least 601 votes from the 1,200-seat Election Committee on March 25, a second round of voting between the top two candidates will be held the same day. If both fail to secure at least half the votes again, a new nomination period will be set and a run-off held on May 6.

This is an edited version of an article that ran in the South China Morning Post on February 29

The Issues

Digging up the dirt

Although most election candidates would deny it, picking on the misdeeds of opponents remains the most commonly used strategy in an election. Here is a recap of the issues that have raised public concern over the integrity of chief executive candidates:

Henry Tang Ying-yen

Tang had been plagued by scandals since early November when reports of his extra-marital affair surfaced. He admitted to cheating on his wife.

But Tang denied allegations he had built illegal structures at his Kowloon Tong residence, saying he had only dug a hole as a store room. Soon, however, the media discovered a luxury basement with a Japanese bath, wine cellar, gym and theatre.

Leung Chun-ying

Leung was accused of being a violent husband who had a romantic relationship with one of his campaign office staff. He was also accused of favouring a business partner in the West Kowloon Cultural District design competition he oversaw. He is facing questions over his possible links to a design entry submitted by a team led by Malaysian architect Ken Yeang. Leung's firm DTZ was listed as a property adviser on the team's submission. Leung was accused of favouring the design. Leung has denied any conflict of interest.

The scandals' impact on public opinion

Jeffrey Lam Kin-fung, a Tang supporter, said Tang's wrongdoing with his illegal structures at home was less serious than Leung's alleged conflict of interest in the West Kowloon design contest. 'Leung's case involves public interest, while Tang's is only a personal one,' he said.

But Tang seems to have been hard hit by the scandals. He has failed to close the popularity gap on his arch-rival Leung significantly.

A poll of 501 residents - co-commissioned by the SCMP and conducted on February 27 and 28 - showed a wide gap in popularity between Leung and Tang. Tang scored 17.7 per cent in a three-horse race while Leung scored 51.2 per cent. The third candidate, Albert Ho Chun-yan, scored 13.3 per cent.

Eric Cheung Tat-ming, a law professor at the University of Hong Kong, said in a RTHK programme on February 25 that candidates must be brave to admit their mistakes if they wanted to regain the public's trust. 'No matter how brilliant the candidates' political programme is, it has no credibility if the candidates themselves lack integrity,' he noted.

Small-circle election

Universal suffrage will not be implemented until 2017.

Cheung says that most citizens dislike the current system of a small-circle election.

'If the citizens are not allowed to cast votes in a chief executive poll, candidates will not have to pay attention to concerns of the public,' he said.

'Instead what they have to care about is the concerns of the 1,200 members of the Election Committee. Under these circumstances, integrity is no longer important and the candidates' political programme seems meaningless.'

Cheung said that allowing people to vote for chief executive candidates directly was the only way to ensure a free and fair election.

Timeline

November 27: Henry Tang Ying-yen announces that he will run for the office of chief executive during a press conference held at the Admiralty MTR station.

November 28: Leung Chun-ying declares his own candidacy at the Convention and Exhibition Centre.

December: Both candidates land in hot water following media reports that question their integrity. It is reported that Tang violated laws by building an illegal basement in his Kowloon Tong home. Leung in turn is criticised for his handling of a controversial West Kowloon arts hub design competition.

February 14: The nomination process for chief executive begins. Democratic Party chairman Albert Ho Chun-yan becomes the first candidate to secure a nomination in the race.

February 27: Legislative Council president Tsang Yok-sing says he will not run for chief executive after all, despite expressing interest earlier.

February 29: Nominations close. Lawmaker Regina Ip Lau Suk-yee fails to win the required minimum of 150 nominations. That makes the election a three-horse race between Tang (390 nominations), Leung (305 nominations) and Ho (188 nominations).

March 23: Dr Robert Chung Ting-yiu, head of the University of Hong Kong's public opinion programme, plans to hold a citywide opinion poll for people's most popular choice of Hong Kong's next leader. Chung said the system was well-tested and could produce credible results.

March 25: Official vote for chief executive.

Voices: What people are saying

'A second round of voting is no good. Whoever came into power [that way] would have very weak authority and the split could spill over to the next election.'

A source familiar with the central government's view

'Recently there has been a suggestion which I think is not healthy ... that the chief executive can even be a stupid person if there are smart people around him.'

Chief Executive candidate Leung Chun-ying

'We are facing unprecedented attacks, which are wolf-like and fierce. But it doesn't mean our rivals will win.'

Chief Executive candidate Henry Tang Ying-yen shortly after his rival Leung Chun-ying submitted his nomination form with his own candidacy