Taiwan\'s presidential candidates kicked off a hectic last day of campaigning Friday, wooing floating voters who will decide the outcome of a tight race watched attentively in Beijing and Washington. The choice in Saturday\'s vote is essentially between the incumbent Ma Ying-jeou, who has overseen four years of improved ties with China, and his main challenger Tsai Ing-wen, a sceptic on closer mainland relations. \"The US and China are both sitting on the edge of their chairs nervous about the outcome of this upcoming election in Taiwan,\" the former de facto US ambassador to Taiwan, Douglas Paal, told the CTI news channel. It is only the fifth time that Taiwan has held democratic elections since 1996, and the race is considered too close to call, with recent surveys showing Ma leading Tsai by as little as three percentage points. With presidential elections looming in the United States and a power transition underway in China, both Washington and Beijing will be keeping a close eye on the poll in Taiwan, which has been a traditional trouble spot. Taiwan has governed itself since 1949, but China claims it as part of its territory, and has never ruled out the use of force to bring about reunification. The constant threat from an ever-more powerful China means mainland policies are always an issue in Taiwan\'s elections, but this time economic matters such as perceptions of a growing income gap have also crept up the agenda. \"The chance to change the future is in our hands tomorrow. We have to use our votes to lead Taiwan\'s democracy to a brand new stage,\" Tsai, who is also vying to become the island\'s first female president, said early Friday. The 55-year-old, who has reportedly caused concern in Washington over her China views, promised stable ties with Beijing as she rode an open-top jeep to canvass voters in the northern city of Keelung. Tsai will spend the entire day in the north, where her anti-China Democratic Progressive Party is relatively weak. President Ma, meanwhile, will cover large parts of the island, including the south, where the ruling Kuomintang (KMT) party faces an uphill struggle. Ma began the day by paying a tearful tribute to late president Chiang Ching-kuo, son of the nationalist leader Chiang Kai-shek, at his shrine in the northern city of Taoyuan. His campaign was given a boost Friday when 127 executives -- many based in the north\'s Hsinchu Science-based Industrial Park, the island\'s \"Silicon Valley\" -- placed an advert in the Apple Daily and Liberty Times giving him their backing. The ad called on voters to support the so-called \"1992 consensus\", a vague formula under which Beijing and Taipei both agree there is only one China. \"Under the current economic circumstances, there is no other option... so that we can feel at ease continuing our business operation and taking care of employees and their families,\" the statement said. The ad was initiated by John Hsuan, the honorary vice chairman of the United Microelectronics Corp, the world\'s second biggest contract microchip maker, according to Hsuan\'s office. Ma has also received backing from Terry Gou, the founder of tech giant Foxconn, and Chang Yung-fa, founder of the island\'s leading transportation conglomerate Evergreen. Both Ma and Tsai will attend mass rallies in Taipei late at night, required by law to end at 10 pm (1400 GMT). An extra factor of uncertainty in this year\'s election is the candidacy of James Soong, a former KMT heavyweight, who has minimal chance of winning but could take crucial votes away from Ma. Saturday\'s presidential vote coincides with an poll for Taiwan\'s 113-member parliament, where the KMT currently has a majority.