Here are key facts on Mr Hsieh, whose ruling Democratic Progressive Party (DPP) lost legislative elections in January:
* Mr Hsieh was born in 1946 and studied law at National Taiwan University. He received a masters degree in law from Kyoto University in Japan.
* His work as a defence lawyer for political dissidents in 1980, considered a turning point for Taiwan's pro-democracy groups under Nationalist Party (KMT) rule, saw Hsieh shoot to political prominence.
* Mr Hsieh was a politically active city council member in Taipei for two terms, from 1981-1988. In 1986 he was involved in the formation of Taiwan's first opposition party, the DPP, by drafting its constitution.
* After serving as a legislator in the early 1990s, Mr Hsieh was elected mayor of Kaohsiung, Taiwan's second largest city, from 1998 to 2005.
* Mr Hsieh was premier under current President Chen Shui-bian from February 2005 to January 2006, when he became the fourth cabinet head to resign since Mr Chen took office in 2000.
* In December 2006, Mr Hsieh lost the mayoral election in Taipei to Hau Lung Bin of the KMT.
* Mr Hsieh's top campaign issues include the environment, the underprivileged and Taiwan's identity. He is more moderate towards China, which considers Taiwan a breakaway province under its 'one China' policy, but hopes to accelerate Taiwan's quest to become a country distinct from China.
* Mr Hsieh has called for gradual opening of Taiwan-China economic links and said in February that he would invite China's President Hu Jintao to Taiwan if elected. -- REUTERS