The secretary-general of Taiwan's Presidential Office, Su Tseng-chang, surprised most observers yesterday by signing on to run for the chairmanship of the ruling Democratic Progressive Party. He also submitted his resignation to President Chen Shui-bian, seen as the man behind Mr Su's abrupt decision. Mr Su is one of four DPP heavyweights in the running to succeed Mr Chen in 2008. His declaration to run for the party post rules him out of the contest for the premiership after the cabinet resigns today. Taiwanese analysts said whoever won the premiership would have a better chance of winning the 2008 presidency as they would have access to government resources. But a presidential source said Mr Su, who is being tipped to win the DPP chairmanship in a party election on January 31, would still have a good chance because he would be able to build up his influence during the local elections before 2008. The mayor of Kaohsiung, Frank Hsieh Chang-ting, is now seen as the most likely successor to Premier Yu Shyi-kun.