Taiwan's local elections are heating up as former President Tsai Ing-wen steps out to back the DPP's Taipei mayoral candidate, a boost for the party's push to retake the capital.

• Puma Shen registers his run for Taipei mayor on September 2, with Tsai Ing-wen at his side.
• It is the first time the two have appeared together in public since he entered the race.
• Tsai warmed up the crowd the night before with a LINE message to Taipei residents introducing "a good friend."
• The campaign is running a photo game letting supporters generate selfies alongside Tsai and Shen.
• The DPP's Taipei city council candidates will register the same day to show a united front.

Outlook: Expect the DPP to lean hard on Tsai's popularity in Taipei as the nine-in-one local election campaign gets going.