Taiwan's two main opposition parties are pushing a joint front ahead of year-end local elections, but their alliance is already cracking in key districts.

• Taichung Mayor Lu Shiow-yen called for a broad opposition alliance covering the KMT, the TPP, and independents.
• TPP chairman Huang Kuo-chang backed the idea fully, accusing the ruling DPP of trampling on Taiwan's democracy and using prosecutors against political rivals.
• The alliance collapsed in Zhubei, where both parties are running their own mayoral candidates in a three-way race.
• Polling in Zhubei shows the KMT candidate narrowly ahead of the DPP, with the TPP candidate a distant third.
• The fallout is spreading: the TPP has threatened to expel members who campaign for the KMT's Hsinchu County candidate, and the KMT barred Taipei Mayor Chiang Wan-an from appearing solo for TPP candidates.

Outlook: Expect more patchwork deals city by city, with Hsinchu and Yilan the biggest risk of the two parties splitting the opposition vote.