Taipei Mayor Wayne Chiang Wan-an faces an unexpectedly tough re-election fight in a race closely watched for its potential to damage the main opposition party Kuomintang and further strain the island’s relations with Beijing. Just five months ago, Chiang appeared comfortably positioned for a second term in a city where the KMT has traditionally enjoyed an advantage over the ruling Democratic Progressive Party. A poll by local cable news network TVBS in late May put him 28 percentage points ahead...