Professor Joseph Cheng Yu-shek, a peace broker at breaking point

As the links between the moderates and radicals of the pan-democratic camp are stretched to breaking point over the issue of universal suffrage, Professor Joseph Cheng Yu-shek is standing bravely in their midst, trying to hold the two allies together.

The Alliance for True Democracy convenor said it looked like his final duty as arbitrator for pan-democrats for more than a decade - and he would not give up. "This is probably my last role as a convenor for the pan-democratic camp. I am, after all, 64 and about to retire," said Cheng, a political scientist at City University.

But hopes of a happy ending in this last chapter of his battle for consensus in the pan-democratic camp and 20 years of endeavours in democratisation could be misplaced.

Wednesday saw the Alliance, which is made up of 26 of the 27 pan-democratic lawmakers, unveil its proposal for electoral reform in the 2017 chief executive election - a proposal hammered out in various meetings and assumed to have been agreed upon.

It suggested a three-track system in which candidates could be chosen by public nomination or through support from political parties.

Those choices would then be rubber-stamped by the nominating committee, the group responsible under the Basic Law for officially nominating candidates.

However, a row immediately erupted between the moderate Democratic Party and the radical People Power over whether all the "tracks" were indispensable.

People Power lawmaker Raymond Chan Chi-chuen accused the Democratic Party of twisting the Alliance's proposal as all "three tracks" were integrated and indispensable.

But Democrat chairwoman Emily Lau Wai-hing said there had never been any consensus on the idea that all three options were a single package.

Both backed their arguments by quoting Cheng.

Cheng's own rhetoric was a study in ambiguity and failed to clarify who was right or who was wrong. "It is no longer our proposal if any of the tracks are taken away," said Cheng on Wednesday. But on Friday, he said: "I have never said [all options are] indispensable."

Cheng is likely to remain non-partisan in the People Power and Democrat face-off, a tactic that has worked before in resolving differences in the increasingly fragmented liberal camp.

In 2004, the academic was the founding moderator of the pan-democrats' coordinating body for district council elections where there had been clashes between factions.

At the time he was convenor of the Power for Democracy, a civil group aimed at fostering political participation and civil rights which he co-found in 2002 with, among others, Democrat Albert Ho Chun-yan and Labour Party lawmaker Lee Cheuk-yan.

Despite his role as spokesman for the pan-democrats, Cheng has never run for public office.

When Civic Party lawmaker Claudia Mo Man-ching was a journalist back in the 1980s, she said Cheng was a "favourite commentator".

He had emerged as the go-to political observer after finishing his postgraduate Chinese political studies in New Zealand and Australia in 1979. That had followed a social science degree at the University of Hong Kong in 1972.

"When I was covering the Sino-British talks over Hong Kong's future, he was the favourite commentator among journalists," said Mo, who worked for TVB back then.

Mo said Cheng's integrity and tolerance made him the best man to try to maintain cohesion in the pan-democratic camp.

"He has an impeccable political network. He is also assertive without being aggressive," said Mo, who went on to set up the Civic Party with Cheng in 2006. "I would not call him an academic. He is a scholar, with integrity."

She added: "There are too many academics who are afraid of offending Beijing."

In contrast, Cheng has often found himself under fire for antagonising Beijing.

The most recent example came last October after he met Shih Ming-teh, a political prisoner in Taiwan for 251/2 years who has also been denounced on the mainland as an advocate for Taiwan's independence.

Cheng's meeting with the former Democratic Progressive Party chairman was amplified by state media and Beijing-loyalists as a step by Hong Kong democrats towards becoming a "separatist force".

Business chambers and pro-establishment lawmakers issued statements condemning Cheng and the two fellow democrats who also attended the meeting - Occupy Central movement organiser Reverend Chu Yiu-ming and Labour Party chairman Lee Cheuk-yan.

Cheng also faced immense pressure over electoral reform before - in 2010, when the pan-democrats were divided over proposals for election arrangements for the 2012 elections.

This time round, Cheng said the lack of distinct leaders in the pan-democratic camp had exerted extra pressures.

"Back in the 1990s, the Democratic Party was the dominant force, and their chiefs, Martin Lee Chu-ming and Szeto Wah were the leaders. But now you have the Civic Party, People Power and more, all with different interests," said Cheng.

He added that the pro-government camp was subject to similar pressures, courtesy of the tensions caused by the prospect of political reform.

He noted Legislative Council president Jasper Tsang Yok-sing came under attack from his own pro-establishment camp last October over his perceived liberal remarks suggesting Hong Kong was at the mercy of "Beijing's will" when it came to introducing universal suffrage in 2017.

"The polarisation and fragmentisation are natural as we stand at the crossroads of constitutional reform," said Cheng.

"Look at Jasper Tsang - he is a pro-government heavyweight yet has had to face severe attacks from other loyalists for his comments."

So why does Cheng endure the pressure from friends, the attacks from enemies and the frequent mentions in pro-Beijing media of a plagiarism controversy which saw him demoted at CityU nearly 20 years ago?

He says it's the plain and simple belief in democracy.

"It is just my whole personal education experience makes me believe we have to have a democratic system."

Professor Joseph Cheng Yu-shek

Age: 64

Family: Married, one son and one daughter

Education:
Bachelor of Social Science, University of Hong Kong (1972)
Bachelor of Arts (Postgraduate), Victoria University of Wellington, New Zealand (1973)
PhD in political science, Flinders University, Australia (1979)

Career:
Assistant lecturer, Chinese University (1977-1989)
The Open Learning Institute of Hong Kong (1989-91)
Full-time member of the government's Central Policy Unit think tank (1991-92)
Professor of political science, City University (1992-)