Taiwan, a neighbouring island China claims as its own, has been a democratic success story since holding its first direct presidential election in 1996, the culmination of decades of struggle against authoritarian rule and martial law.
The ruling Democratic Progressive Party (DPP), which champions Taiwan's separate identity and rejects China's territorial claims, is seeking a third term in office with its candidate, current Vice President Lai Ching-te.
China, which has never renounced the use of force to bring Taiwan under its control, has framed the elections as a choice between "peace and war", calling the DPP dangerous separatists and urging Taiwanese to make the "right choice".
The DPP rejects China's sovereignty claims, and says only Taiwan's people can decide their future.
In the run-up to Saturday's election, China repeatedly denounced Lai and rebuffed repeated calls from him for talks.
China's defence ministry, responding to a question on Friday on Taiwan's air force upgrading F-16 fighter jets and buying more from the United States, said even with purchases of U.S. weapons the DPP "cannot stop the trend of complete reunification of the motherland".
"The Chinese People's Liberation Army remains on high alert at all times and will take all necessary measures to resolutely crush any form of 'Taiwan independence' separatist plots and firmly defend national sovereignty and territorial integrity," said ministry spokesperson Zhang Xiaogang.
Lai says he is committed to preserving peace across the Taiwan Strait, but has accused China of seeking to interfere in the vote by spreading disinformation and putting further military and economic pressure on the island which Beijing views as "sacred" Chinese territory.
CHINA LOOMS LARGE
Lai is facing two opponents for the presidency - Hou Yu-ih of Taiwan's largest opposition party the Kuomintang (KMT) and former Taipei mayor Ko Wen-je of the small Taiwan People's Party (TPP), only founded in 2019.
No matter who wins, China looms in the background.
Taiwan's government believes China is likely to attempt to put pressure on its incoming president after the island votes, including staging military manoeuvres near the island this spring, two senior government officials said.
Hou wants to re-start engagement with China, beginning with people-to-people exchanges, and has, like China, accused Lai of supporting Taiwan's formal independence. Lai says Hou is pro-Beijing, which Hou rejects.
The KMT and TPP say Taiwan needs a change of government after eight years of DPP rule, though an effort by the two parties late last year to form a joint ticket to take on the DPP collapsed in acrimony.
The DPP and KMT will both hold their final rallies Friday evening in Taipei's neighbouring New Taipei, while the TPP has the prime spot in central Taipei near the presidential office. Tens of thousands are expected to attend each event.
The DPP and KMT alike face a formidable challenge from the TPP, seeking to break the mould of two-party politics.
"This political status quo has led to an increasing wave of people hoping for reform. It has also pushed the TPP, which represents Taiwan's third force, on to the stage of Taiwan's politics," the TPP's Ko told foreign reporters in Taipei on Friday.
Ko has won a passionate support base, especially among young voters, for focusing on bread and butter issues like the high cost of housing. He also wants to re-engage China, but insists that cannot come at the expense of protecting Taiwan's democracy and way of life.
"We are not afraid" of China, said tech worker Charlie Lee, 61. "We already have a very strong democratic identity and will fight to the end."
Polls open at 8.00 a.m. (0000 GMT) and close at 4.00 p.m. (0800 GMT), with ballot counting by hand starting almost at once. There is no electronic, absentee, proxy or early voting.
The result should be clear by late evening Saturday when the losers concede and the winner gives a victory speech.
Tsai is constitutionally barred from standing again after two terms in office.
