He was accused of being a spy for China and had to resign as a senior official in Taiwan's agency overseeing cross-strait affairs two years ago. But that has not deterred Kuomintang (KMT) veteran Chang Hsien-yao, 52, who maintains his innocence, from seeking a seat in Saturday's legislative polls in Kaohsiung, the island's second-largest city.

Neither is his brush with the law his biggest trial. He shook off those spy allegations after all charges were eventually dropped.

Instead, he is facing his toughest test battling Democratic Progressive Party (DPP) candidate Liu Shih-fang, 57, for control of the Zuoying-Nanzih district. With some 300,000 voters, it has stayed solidly in the blue camp, the KMT-led coalition, in the last 60 years, in a sea of green, the colour of the DPP that dominates southern Taiwan.

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But things are not so certain now for the KMT. A recent poll by broadcaster TVBS put Ms Liu seven percentage points ahead of Mr Chang, with about a quarter of voters undecided. KMT's internal polls have shown that the vote is evenly split.

Admitting to the uphill task, Mr Chang said: "When I meet the residents, I can see that they are upset with how the (island) and their lives have turned out. I can feel that they no longer trust the KMT."

Ms Liu is banking on her credentials as Kaohsiung's former deputy mayor and the momentum that the DPP is currently riding on to unseat the KMT, whose incumbent Huang Chao-shun is being fielded in the at-large legislative race.

Situated in the north of Kaohsiung, the district has a population made up mostly of mainlanders - Taiwanese who fled China in 1949 after the KMT defeat by the communists there. Their fraught history has made many of them KMT loyalists. Young people, who are usually less sentimental, make up about 6.6 per cent of the district's voters.

So this is shaping up to be one of the hottest races in Kaohsiung, with both candidates going door-to-door to canvass for votes.

Mr Chang, known as the "Blue Superman" in his campaign, hopes to tilt the balance in his favour. "I want (voters) to know that I'm a straight talker... I will speak my mind and do what I think is right, even if it gets me into trouble."

He has to win over those who are frustrated with the ruling KMT, for what they see as its poor performance. Many are also hit hard by a stagnating economy, low salaries and skyrocketing housing prices.

Among the disgruntled voters is technician Su Tian-lai, 35,who has voted for the KMT in the last three legislative polls but is now undecided. He said: "It's difficult to make ends meet when I spend more than half of my monthly pay to service my mortgage.

"I may not even be bothered to vote. All these politicians can make all the promises now, only to break them later."

DPP, which runs Kaohsiung, also comes in for some flak but is trying to appease such voters, reminding them that a recent poll shows seven in 10 of the port city's denizens are satisfied with its performance.

DPP campaign manager for Kaohsiung Chen Chi-mai said: "(The KMT) have had eight years to get things right. But they made things worse. Enough is enough."

Still, there are staunch KMT supporters who see the good work Mr Chang had done as lawmaker in 2008-2012 in the now-defunct Kaohsiung ward.

Retiree Yuan Chuan Rong, 70, said: "He made life better for us then. He has his heart in the right place. Without the KMT, we would not have the Taiwan you see today."