As if the United States didn’t already have enough foreign policy worries, a dangerous issue that has been mercifully quiescent over the past five years shows signs of reviving. Taiwan’s governing Kuomintang Party (KMT) and its conciliatory policy toward Beijing suffered a brutal defeat in elections for local offices on November 29. Indeed, the extent of the KMT’s rout made the losses the Democratic Party experienced in U.S. midterm congressional elections look like a mild rebuke. The setback was so severe that President Ma Ying-jeou promptly resigned as party chairman. Although that decision does not change Ma’s role as head of the government, it does reflect his rapidly declining political influence.

As I discuss in an article over at The National Interest Online, growing domestic political turbulence in Taiwan is not just a matter of academic interest to the United States. Under the 1979 Taiwan Relations Act, Washington is obligated to assist Taipei’s efforts to maintain an effective defense. Another provision of the TRA obliges U.S. leaders to regard any coercive moves Beijing might take against the island as a serious threat to the peace of East Asia.

During the presidencies of Lee Teng-hui and Chen Shui-bian from the mid 1990s to 2008, Beijing reacted badly to efforts by those leaders to convert Taiwan’s low-key, de facto independence into something more formal and far reaching. As a result, periodic crises erupted between Beijing and Washington. U.S. officials seemed relieved when voters elected the milder, more conciliatory Ma as Chen’s successor. That political change also seemed to reflect concern on the part of a majority of Taiwanese that Chen and his explicitly pro-independence Democratic Progressive Party (DPP) had pushed matters to a dangerous level in testing Beijing’s forbearance.

But just as Chen may have overreached and forfeited domestic support by too aggressively promoting a pro-independence agenda, his successor appears to have drifted too far in the other direction. Domestic sentiment for taking a stronger stance toward the mainland on a range of issues has been building for at least the past two years. Public discontent exploded in March 2014 in response to a new trade deal between Taipei and Beijing, which opponents argued would give China far too much influence over Taiwan’s economy. Those disorders culminated with an occupation of Taiwan’s legislature, accompanied by massive street demonstrations that persisted for weeks. The November election results confirmed the extent of the public’s discontent.

Perhaps reflecting the shift in public sentiment toward Beijing, even Ma’s government began to adopt a more assertive stance on security issues, despite pursuing enhanced economic ties. Taipei’s decision in the fall of 2014 to spend $2.5 billion on upgraded anti-missile systems reflected a renewed seriousness about protecting Taiwan’s security and deterring Beijing from contemplating aggression.

China’s reaction to the November election results was quick and emphatic. Chinese media outlets cautioned the victorious DPP against interpreting the election outcome as a mandate for more hard-line positions on cross-strait issues. Even more ominous, Retired General Liu Jingsong, the former president of the influential Chinese Academy of Military Sciences, warned that the Taiwan issue “will not remain unresolved for a long time.” Moreover, Chinese officials “will not abandon the possibility of using force” to determine the island’s political status. Indeed, he emphasized that it remained an option “to resolve the issue by military means, if necessary.” That is a noticeably different tone from Deng Xiaoping’s statement in the late 1970s that there was no urgency to deal with the Taiwan issue—that it could even go on for a century without posing a serious problem.

A key question now is whether Beijing will tolerate even a mildly less cooperative Taiwan. Chinese leaders have based their hopes on the belief that greater cross-strait economic relations would erode Taiwanese enthusiasm for any form of independence. That does not appear to have happened. Opinion polls indicate meager support for reunification with the mainland—even if it included guarantees of a high degree of political autonomy.

But the adoption of a confrontational stance on Beijing’s part regarding Taiwan would quickly reignite that issue as a source of animosity in U.S.-China relations. The Obama years have already seen a worrisome rise in bilateral tensions. The announced U.S. “pivot” or “rebalancing” of U.S. forces to East Asia has intensified Beijing’s suspicions about Washington’s motives. Sharp differences regarding territorial issues in the South China and East China seas have also been a persistent source of friction. The slumbering Taiwan issue is now poised to join that list of worrisome flashpoints.