Taiwan's year-end local elections will test decades-old party strongholds, and the results will shape the 2028 presidential race.

• The DPP has ruled Tainan, Chiayi County, Pingtung and Kaohsiung for 25 to 33 years straight, forming a green wall across the south.
• The KMT's safest seats are Miaoli, held by the blue camp for 75 years, plus Lienchiang, Hualien and Taitung.
• Hsinchu County is one to watch: the DPP candidate Cheng Chao-fang is the son of a former KMT county chief, which could crack a 25-year blue hold.
• New Taipei, Taiwan's biggest city and blue-run for over 20 years, faces a strong DPP challenge from Su Chiao-hui.

Outlook: Whichever camp breaks into the other's heartland will head into 2028 with the momentum.