TAIPEI • Taiwan's President Tsai Ing-wen has seen off an unprecedented challenge to her leadership from within her own party, defeating her former premier in the ruling Democratic Progressive Party's (DPP) primary ahead of January's presidential election.

Ms Tsai, 62, secured a majority support in the telephone poll this week, DPP spokesman Lee Yen-jong said yesterday .

Her challenger, former premier Lai Ching-te, 59, is an outspoken proponent of formal independence for Taiwan.

Ms Tsai hails from the more moderate wing of her pro-independence party. She still requires approval from the party's executive committee next week to officially become the DPP's nominee.

"We have come up with the strongest candidate for the Taiwanese people," Mr Cho Jung-tai, DPP chairman, told reporters. He urged the party to unite after the months-long race was marked by heated exchanges between Ms Tsai's administration and Mr Lai.

Ms Tsai's victory grants her something of a reprieve after waning public support culminated in her party's devastating losses to the opposition Kuomintang (KMT) in regional elections last November.

Concerns that she would be unable to win a second term in next year's presidential election spurred her premier to resign and challenge her for the DPP's nomination.

But despite the rebound in her support, she still faces a test to avoid becoming Taiwan's first one-term president.

Five hopefuls are vying for the KMT nomination to run against her, including the populist mayor of Kaohsiung City, Mr Han Kuo-yu, and Foxconn Technology Group's billionaire founder Terry Gou.

Taipei City Mayor Ko Wen-je is also considering a bid as an independent.

The DPP's primary was different than most, relying on independent surveys of the general public - instead of voting - to determine which of the two contenders would fare better in the upcoming election. The party and four polling companies surveyed 15,000 adults, asking who they would prefer in a hypothetical three-way race including Mr Han and Dr Ko.

Ms Tsai outperformed Mr Lai in the survey, which appeared to be an effort to find out who could mount a stronger challenge against Mr Han, seen as the opposition's strongest candidate.

Ms Tsai told reporters: "My most important responsibility now is to unite all forces... to protect Taiwan's democracy, to defend the fruits of reforms and to solidify our national sovereignty."

She was elected in 2016 as the island's first female leader, defeating the China-friendly KMT, which oversaw an unprecedented thaw in cross-strait ties but began to unnerve many voters with its perceived cosiness with the mainland.

In a Facebook post on Wednesday, Ms Tsai referenced events in Hong Kong, where people are protesting against plans to allow extraditions to the mainland.

"Look at Hong Kong and think about Taiwan, every single Taiwanese has to join hands to fight against those people who want to destroy our national sovereignty or sacrifice freedom and democracy for temporary benefits," she said.

BLOOMBERG, AGENCE FRANCE-PRESSE