Madame President? Taiwan's leading candidate quietly defies China.

Tsai Ing-wen is 20 points ahead in polling for the Jan. 16 national election. A political landslide could put the Nationalist Party completely out of power for the first time in 70 years.

“Our next president!” gushes a visitor to Tsai Ing-wen's campaign headquarters, pointing to a giant portrait of the candidate. “No one can stop her this time.”

With sky high expectations among her supporters, and polling numbers to match, Ms. Tsai – a former law professor whose lack of flashy persona is more than compensated for by a quiet sophistication and steely determination – has the indisputable momentum in Taiwan's presidential campaign. 

A month ahead of the Jan. 16 election, Tsai and the Democratic Progressive Party (DPP) she leads are overwhelming favorites to win the island republic's top office. Her campaign slogan, “Light up Taiwan,” underscores a platform clearly favoring interests seen from Taipei rather than Beijing.

Tsai is the super-achieving youngest of 11 children whose father, Tsai Jie-sheng, was a successful entrepreneur and investor. Her sprawling family mirrors Taiwan’s own complex society, with siblings scattered from Taiwan to California. The home was a lively one where she early learned about social diversity, and business and current affairs.

"She's a careful decisionmaker,” says Su Tzen-ping, founder of the news site New Talk. “She's a good listener and likes to consider all sides of an issue before coming to a conclusion.”

Last-minute mudslinging

Mr. Su says Tsai’s large circle of friends, including leaders from Taiwan’s high-tech and finance communities, gives her a different profile than current President Ma Ying-jeou, who is often seen as isolated from society and with few trusted friends outside politics.

Next month's national election here is hardly a done deal. Last-minute mudslinging has erupted among politicians from the ruling Nationalist Party or Kuomintang (KMT). Opinion polls can be notoriously wrong, as they were before Britain's parliamentary elections earlier this year.

Still, Tsai's main opponent, Eric Chu of the KMT, is trailing by more than 20 points in most polls. His party’s top ranks are rife with personal feuds, and the Taiwan economy is stumbling. Public discontent runs deep.

Across the island, the mood is eagerness for change. That’s a contrast with 2012, when Tsai lost to President Ma after a bruising campaign – still, however, garnering an impressive 46 percent of the vote.  

If polls and surveys are reliable, however, there is enough momentum to push the KMT completely out of power for the first time since it took refuge on the island 70 years ago. In addition to the presidency, if the DPP and other opposition parties win control of the legislature, it could open a wide window for social and political reforms and move Taiwan's relations with China onto untested ground.  

At center stage in the drama is Tsai, a Western-educated legal scholar yet to be elected to public office in her own right. She is not part of the founding generation of Taiwan’s democratic era. Rather, she presents an unusual profile of a deliberative figure in a political culture where passionate rhetoric and ego-heavy personalities are more typical.

Few doubt Tsai's grit and determination to be president, but some supporters ask whether she has the boldness needed of a leader in difficult times.

Policy wonk without peer

Unlike most Taiwanese politicians, she is a genuine policy geek.

“Tsai has participated in nearly every policy discussion in her party for the past eight years,” says Su, of New Talk. Her reputation on policy is without peer, he says, though she has a knack for dodging the issues.

Tsai has worked in senior government posts on and off for three decades. A graduate of National Taiwan University, Cornell University, and the London School of Economics, she made her reputation negotiating Taiwan's entry into the World Trade Organization and as adviser to two presidents on the fraught issue of relations with China.

She also served in senior posts under former DPP president Chen Shui-bian.

Unlike many of Asia's woman leaders who come from family dynasties, she is the first and only member of her extended family to enter politics.

Tsai's political career has been a hard slog. Her main achievement was taking the reins of the DPP after Mr. Chen was prosecuted – some say he was persecuted by the KMT. He was convicted on corruption charges in 2008 and sent to prison.

As a willing listener in a big-tent party, Tsai is credited with restoring morale and working with other DPP leaders to rebuild the party. She worked to deepen areas such as judicial reform, energy policy, civic rights, and national security, and earned a reputation as a relentless campaigner.

Tearful loss four years ago

After her first run for president four years ago, she conceded defeat to Ma on a rainy December night. With other DPP leaders standing glumly by, Tsai promised thousands of tearful voters that she would come back in 2016 to carry out their progressive agenda.

Since then, Tsai has mastered retail politics, observers say. “This time around [Tsai] has a different personality,” says Li Chun-yi, a DPP lawmaker from southern Taiwan. “She's confident to deal with the crowds. She even lets people touch her, whereas before she protected her personal space and kept a physical distance from supporters.”

Tsai has identified her leadership as closer to Germany's Angela Merkel than Britain's Margaret Thatcher.

“She has wanted to model herself as the Angela Merkel of the East – strong-willed, decisive, and easy to communicate with others,” says Lai I-chung of Taiwan Thinktank, an opposition-friendly policy research institute.

If elected she will face serious challenges in keeping Taiwan on a democratic path and in reversing a sluggish economy.

Tsai and her supporters are wary of the KMT's views about China. She especially questions Ma's push to integrate the two economies and hold political talks with Beijing under a doctrine known as “one China.”

Yet Tsai's campaign avoids the volatile rhetoric of independence that former president Chen engaged in, opting instead to celebrate Taiwan’s distinct culture and 23 million people. Slick infomercials and music videos with sentimental images of Taiwanese society and the island's stunning geography send a nuanced message of quiet defiance.

Analysts place Tsai firmly in the “green” camp of domestic politics that champions democracy and national sovereignty. “Tsai always says that we will only negotiate with China as an equal and that we govern ourselves; she's very clear on this,” says Lo Fu-chen of the World United Formosans for Independence, a formerly banned group that advocates independence of China. “We fully trust her.”

Taiwan's iconic Marxist historian and prodigal revolutionary, Shi Ming, agrees. “She's plain and unpretentious, a woman of the people,” says Mr. Shi, who returned from Japan after four decades in exile agitating against KMT rule. “Right now, there's no other presidential talent in Taiwan but her.”