Once a dominant political force, Taiwan’s main opposition party lost the last two presidential elections in large part because it has promoted closer ties with China. Now, faced with voters who have been alarmed by Beijing’s aggression toward the island, the Kuomintang is placing its hopes on a new type of candidate: a popular local leader with a blank slate on the thorny question of China.

The Kuomintang, or Nationalist Party, on Wednesday nominated as its presidential candidate Hou Yu-ih, a 66-year-old, two-term mayor of New Taipei City and former police chief who has tried to strike a middle ground within the Kuomintang on the island’s relations with China. Mr. Hou launched his bid with a rallying call.

“We must unite for victory, especially at this stage when our country is facing fierce and dangerous international circumstances,” Mr. Hou said following the announcement of his nomination.

His candidacy sets the stage for a tight race next January that could chart a new course for Taiwan in the big-power standoff between China and the United States and reshape tensions around the Taiwan Strait, one of the world’s most dangerous flash points. Under the seven-year leadership of President Tsai Ing-wen of the governing Democratic Progressive Party, Taiwan has come under intensifying military and diplomatic pressure from China and pushed back by bolstering ties with the United States.

Within the Kuomintang, Mr. Hou is regarded as a capable administrator with broad appeal, who “would generate the least internal party controversy, align with the general expectations of society and have the highest likelihood of winning in the presidential election,” said Huang Kwei-Bo, a professor of international relations at the National Chengchi University and a former deputy secretary-general of the Nationalist Party.

Mr. Hou’s nomination pits him against Lai Ching-te, the governing party candidate and current vice president. A win for Mr. Lai would likely mean a continuation of China’s policies to freeze out Taiwan from any high-level engagement, as well as Taiwan’s continued closeness with the United States. A victory for Mr. Hou and the Kuomintang could reopen communication channels with China and tamp down military tensions, potentially reducing the pressure on Taiwan to strengthen ties with Washington.

Mr. Hou faced tough competition from Terry Gou, the founder of the iPhone and electronics manufacturer Foxconn, who failed despite holding rallies around the island to make his case for nomination. Analysts said Mr. Gou’s lack of experience in politics and his business interests in China made him an unviable candidate for the Kuomintang.

The Kuomintang in recent years has struggled to balance its China-friendly leanings with the Taiwan population’s souring sentiment toward Beijing. That juggling act has been complicated by Beijing’s crackdown on Hong Kong in 2019 and its ramped-up military drills around Taiwan. The governing D.P.P. has positioned itself as a defender of Taiwan’s sovereignty and democracy, and pointed to Russia’s invasion of Ukraine as an example of the urgent threat of authoritarian expansionism.

But the Kuomintang scored big last year, prevailing in almost two-thirds of local mayoral elections contested, races in which geopolitics matter less than bread-and-butter issues. Mr. Hou handily won his re-election as mayor and has since topped multiple polls within the party for the candidacy.

Unlike most politicians in Taiwan, Mr. Hou began his career as a police officer, in the 1980s. He rose through the ranks and was a key investigator into the 2004 assassination attempt against President Chen Shui-bian. In 2006, Mr. Chen’s administration promoted Mr. Hou to the position of chief of the island’s police force, the youngest officer ever to serve in the role.

In his turn to politics in 2010, he joined hands with Eric Chu, who was then the mayor of New Taipei City. Mr. Hou served as the deputy mayor under Mr. Chu and succeeded Mr. Chu as mayor in 2018. Mr. Chu is now the chairman of the Kuomintang.

Supporters of Mr. Hou in New Taipei City say that he takes real actions to improve the lives of residents. Jax Chen, a 28-year-old nonprofit worker, referred to Mr. Hou’s effort to transform a giant, decades-old garbage dump into green park space as one example.

“In Taiwan’s political scene, it seems like everyone is just talking too much,” he said. “But if there is a person who is pragmatic with capabilities to enforce policies, I believe it would be great and everyone would be willing to accept the person.”

Less well established are Mr. Hou’s views on major geopolitical questions such as how Taiwan should navigate its relationships with China and the United States. China claims Taiwan as its territory, to be absorbed with force if necessary, and accuses the D.P.P. of seeking formal independence. The Kuomintang has asserted that it is the party with the best chance of engaging China and avoiding war.

In an apparent effort to thread the needle, Mr. Hou has said he both opposes Taiwan independence and the “one country, two systems” formulation proposed by China to absorb Taiwan. The position eschews two extremes but leaves open a huge number of possible viewpoints on the existential issue of cross-strait relations.

The lack of clarity about his stance on China has already been criticized by some observers, a potential disadvantage for him on top of his lack of experience in foreign affairs, said Paul Chao-hsiang Chu, a politics professor at National Taiwan Normal University who studies party politics and voters’ behavior.

At the same time, Mr. Hou’s reticence could make him more appealing to centrist voters, said Liao Da-chi, an emeritus professor of political science at the National Sun Yat-Sen University. That is in contrast to Han Kuo-yu, the Kuomintang’s presidential candidate in 2020, who made rousing speeches and pledged to restore closer relations with China but lost in a landslide to President Tsai.

Overall, Mr. Hou has had very few interactions with the United States, said Bonnie Glaser, a Taiwan expert and managing director of the Indo-Pacific program at the German Marshall Fund of the United States. Mr. Hou has said that he has met with officials at the American Institute in Taiwan, the de facto embassy for the United States, at least eight times. But American congressional delegations to Taiwan since its reopening have not been able to meet with him.

As Beijing stokes tensions in the Taiwan Strait, the Kuomintang’s contact with China has sometimes put it in an awkward position.

Earlier this year, just as President Tsai traveled to the United States, Ma Ying-jeou, a former president of Taiwan and an influential leader in the Kuomintang, headed for China on an unofficial trip. Mr. Ma was criticized in Taiwan for appearing to kowtow to China on an inappropriately timed visit. (In retaliation for Ms. Tsai’s visit to the United States, China sent record numbers of military aircraft, as well as naval ships and an aircraft carrier, near Taiwan to conduct military drills.)

“To win the election, it is imperative for the Kuomintang to persuade the people that voting for them is the safer and more promising choice in achieving peace,” Dr. Chu said. “At the same time, how it would convince the Taiwanese people they will not betray Taiwan or allow China to completely swallow up Taiwan’s sovereignty presents a significant challenge for Kuomintang.”