There might be a lesson in Taiwan for political parties in democratic states elsewhere about what to do when stuck with a bad candidate and an approaching election. Taiwan, where politics is always about survival, will elect a new president in January and the ruling Kuomintang, direct descendants of Chiang Kai-shek’s Nationalists who fled the Mainland Communists in 1949, was saddled with a nominee running 20 percentage points behind in the public-opinion polls.

So the party changed nominees. At an extraordinary party congress, the Kuomintang, or KMT, recruited the party chairman and the mayor of New Taipei city, a suburb of the capital, as a new nominee. Eric Chu, a onetime accounting professor and the new nominee, will face Democratic Progressive Party candidate Tsai Ing-wen, who proposes formal independence for Taiwan instead of the current ambiguous de facto autonomy.

The KMT, which once ruled everything on the island with a very firm hand, is trying to recoup its strength after disastrous parliamentary elections a year ago, when it paid a price for several deals it made with mainland China. The KMT, the business establishment and academic economists, defended the deals as necessary to improve a lackluster economy. Cheap labor on the mainland typically assembles machines of various sizes from components made in from Taiwan, and re-exported. But as the mainland economy has slumped from record-breaking decades of rapid growth, Taiwan is turning again to Southeast Asia and the United States.

The government in Beijing gets along with the current president in Taiwan, Ma Ying-jeou, but he is constitutionally barred from election to a third four-year term. Mr. Ma’s administration signed 23 agreements with China to promote investment, tourism and trade, and tension between Beijing and Taipei has eased to the lowest level in more than 60 years.

However, the mainland meddling in Hong Kong, despite its political autonomy enshrined in the 1997 British agreement to turn the colony back to China, has raised suspicion of Beijing’s good faith elsewhere. Last year the Sun Flower Movement, a coalition of students and political activists, occupied the Taiwan parliament and government offices, demanding detailed parliamentary scrutiny of the 2013 Cross-Trade Service Agreement Mr. Ma signed with Beijing.

It’s not clear what comes next. Chinese President Xi Jinping has imposed the most stringent crackdown on political activists and the media in several decades as he struggles to concentrate power in his hands rather than in the Communist Party. Bringing Taiwan and the Singkiang Uighur and Tibetan dissidents under mainland control has been one of Mr. Xi’s major goals.