The opposition Democratic Progressive Party (DPP) has nailed down candidates for the year-end municipality mayoral elections in Taipei, Xinbei, Tainan and Kaohsiung, while its nomination for Taichung remains undecided, party officials said. The party will recruit former Premier Su Tseng-chang to join the battle for Taipei and Yu Shyi-kun -- also a former premier -- to run in Xinbei City, according to top-ranking DPP members. The party is scheduled to complete its nominations by May 19. The elections will be the first of their kind in Taiwan after the government upgrades Taipei County to a special municipality and merges Taichung City and county, Kaohsiung City and county, and Tainan City and county. After the changes, the new municipalities will have the same status as Taipei City and Kaohsiung City. Taipei County will be renamed Xinbei City after its upgrading is formalized late this year. Last week, the DPP used public surveys to select incumbent Kaohsiung Mayor Chen Chu as its candidate for mayorship of the southern Taiwan municipality. Meanwhile, Legislator Lai Ching-te was set to represent the party in Tainan after he beat out his rivals in a public opinion survey. The DPP members revealed that the party is trying to persuade Secretary-General Su Jia-chyuan to join the election in Taichung, but said he didn't appear to be interested in joining the race. According to people close to Su, he is 'cautiously weighing' whether or not to take part in the Taichung election. 