At a talk with university students last month, Taiwan opposition candidate Hou Yu-ih was pushed to define a cornerstone of U.S.-China relations that’s maintained peace on his island for decades.

Instead of outlining the contours of Washington’s one-China policy, the mayor and former policeman avoided the question by citing the need to follow the constitution. "The relationship between the two sides of the Taiwan Strait is clear. We don’t need to get it confused,” he added.

His failure to articulate a critical policy at the bedrock of Taiwan’s international status drew widespread criticism online. It also reflected a key voter concern, namely that Hou lacks the expertise to lead in one of the biggest geopolitical flashpoints in the rivalry between Washington and Beijing.