Turnout among the 15.46 million eligible voters is expected to run as high as 70 percent in a race considered too close to call.
China considers Taiwan a renegade province.
China and Taiwan split after the country's civil war in 1949, and Beijing has repeatedly threatened to invade if the island tries to break away permanently. Its electoral support has been split by the candidacy of Soong, who quit the Nationalists to launch a rebel bid on an anti- corruption platform. As saber-rattling picked up across the Taiwan Strait, Chen has downplayed his support for independence, though his party platform endorses it. Lien has warned that Chen's election could lead to war with the mainland, while Soong has tried to portray himself as a candidate who can make peace with Beijing. Nationalists try to capitalize on fear of China Campaigning in his hometown of Tainan, the Nationalists' Lien reminded voters that under his party's rule the island of 23 million built one of the world's richest economies.