TAIPEI -- Han Kuo-yu, the Beijing-friendly mayor of Kaohsiung, has won the nomination of Taiwan's opposition Kuomintang to challenge incumbent Tsai Ing-wen in January's presidential election.

The KMT said on Monday that Han's approval rating was 44.8%, higher than that of rival Terry Gou, the billionaire founder of Foxconn. Gou obtained a 27.7% rating, ahead of former New Taipei mayor Eric Chu. The weeklong nationwide telephone poll included both KMT members and nonmembers.

"I will be very sincere and seek to visit Foxconn Chairman Terry Gou as well as Eric Chu today right after this news conference, and I hope to do my best to unite the KMT," Han said on Monday after the primary result was announced.

Han said that he would continue to serve as Kaohsiung's mayor and focus on his work in the southern Taiwanese port city. Asked about his stance on China and foreign policy, Han said he would find another time to talk about those topics.

Gou offered congratulations to Han in a statement Monday afternoon. He did not address speculation he might challenge Han and Tsai as an independent.

The billionaire, popular among younger voters, had criticized the primary organizers for omitting cellphones from the telephone poll, suggesting that it would distort the results in favor of his opponents.

But with his congratulatory statement, Gou signaled that he accepted the results.

"I always ask myself what I can do for this beloved land," Gou said in his statement, without indicating whether he will continue his run for the presidency in a different form.

However, his 17-point defeat to Han is hard to ignore. Furthermore, if Gou were to run as an independent, it may divide the KMT support base and work in favor of President Tsai, who represents the independence-leaning Democratic Progressive Party.

Some observers predict that Beijing will pressure Gou not to run, due to such circumstances.

The primary results will be reviewed by the KMT Central Standing Committee on July 17 and delivered to the party's national convention for final approval on July 28, according to KMT Chairman Wu Den-yih.

Surveys had earlier showed Gou gaining ground to catch up with Han. Gou had claimed that Taiwan's economy would top that of South Korea if he became the leader of the island. But some suggested that Gou may have lost momentum amid the flurry of television campaign ads he paid for, which may have made some voters uncomfortable with his use of money as a political weapon.

Han, on the other hand, kept his support from those upset about economic inequality. Many on the internet had even said that they would not vote for the Kuomintang unless Han became the candidate, which might have caused some Gou supporters to shift to Han.

Han, center, poses for pictures at a signing ceremony on a trip to Xiamen in China's Fujian province in March. © Reuters

The recent protests in Hong Kong have caused more Taiwanese to worry about risks from the island drawing closer to China. This momentum has caused the KMT to lose ground to Tsai and the DPP. A poll by broadcaster TVBS at the end of June put Tsai more than 10 percentage points ahead of both Han and Gou.

Born in 1957, Han went to a military academy in his youth, but later went on to major at university in English literature and earn a master's degree in East Asian studies. He first entered politics in 1990 as a county councilor and later was served as a national lawmaker for eight years. There he earned a reputation for his combative personality, going as far as punching former President Chen Shui-bian in a debate.

Han left politics for about a decade after losing reelection in 2001. Eleven years later, he was appointed as general manager of Taipei Agricultural Products Marketing, a little-known organization that oversees the distribution of farm produce.

His pro-China views meant that few people gave him a chance of becoming mayor in Kaohsiung, a city in the south that had been controlled by the DPP for decades.

However, his blunt speaking style and pitch to "show Kaohsiung the money" gained him a group of fans and put him on a meteoric rise to become a new political star. His popularity even triggered a spillover effect that helped other KMT candidates secure 15 mayoral posts in 22 cities and counties across Taiwan last November. The opposition's landslide win led Tsai to step down as DPP party leader.

But Tsai is now trying to leverage the current U.S.-China trade tensions to boost her domestic support. She is on a 10-day trip to the Caribbean, with stopovers in New York and Denver. Her visit comes just days after the U.S. Department of Defense approved a $2.2 billion arms sale to Taiwan.

"The recent American arms sale approval and Tsai's stopovers in the U.S. show closer ties between Taiwan and the country," said Ian Tsung-yen Chen, an assistant professor at National Sun Yat-sen University. "I don't recall any Taiwanese president staying so many days during their transits in the U.S., which is definitely a plus to Tsai's reelection campaign."

Han's previous pledge to build closer economic ties with China helped him win in Kaohsiung, but this now makes him more vulnerable.

Taiwan President Tsai Ing-wen speaks at the Taipei Economic and Cultural Office in New York during her visit to the U.S. on Thursday. © Reuters

The outspoken mayor visited China soon after taking office late last year and met with officials of the Chinese government's liaison office in March in Hong Kong. This raised questions at home about his support for the "one country, two systems" principle under which Hong Kong returned to Chinese rule in 1997.

When hundreds of thousands of Hong Kong citizens took to the streets last month to protest against a proposal to ease the extradition of criminal suspects to China, Taiwan and elsewhere, Han's initial reply when asked his view was "I don't know."

This raised further suspicions about his will to protect democratic Taiwan from the Chinese Communist Party, and he later said that the Hong Kong government should consider suspending the proposal.

"Whether the [Hong Kong issue] continues to be a topic of conversation in the election campaign or will be forgotten depends more on what occurs in Hong Kong and what other policy choices China makes in the coming months," said Ross Darrell Feingold, a Taipei-based lawyer and political risk consultant.

Tsai will be able to attack Han on two fronts: his stance on China and his desire to run for president only months after being elected city mayor, according to Feingold.

Relations between Taipei and Beijing have soured since Tsai took office in May 2016. China, which views Taiwan as a wayward province, has pushed several countries to cut diplomatic ties with the self-ruled island, constantly conducted military drills, and slowed approvals for tourist trips to Taiwan.

"Han's advantage in competing against Tsai is playing the card of Taiwan's economic growth," said National Sun Yat-sen University's Chen. "But when it comes to protecting Taiwan's sovereignty from China, Tsai has the upper hand to secure more public approval."

Sean King, a scholar with the University of Notre Dame's Liu Institute for Asia & Asian Studies, said that the Hong Kong protests have put the KMT on the defensive. "Mainland Chinese President Xi Jinping's increasingly hard line on Taiwan only helps Tsai at home," he said.

Nikkei staff writer Kensaku Ihara contributed to this report.