Image copyright AP Image caption Taiwan goes to the polls Saturday to elect one of the three presidential candidates

Taiwan's three presidential candidates are on their final campaign push before the island goes to the polls Saturday.

President Ma Ying-jeou, seeking a second term, is neck-and-neck with opposition leader and Taiwan's first female presidential candidate, Tsai Ing-wen.

A third contender is James Soong, who observers say could take votes away from Mr Ma.

The race is being closely watched, not least by China and the United States.

Local election watchers are predicting a turn-out of 76 to 80% of the more than 18 million registered voters on the island.

On Thursday night, the candidates made public appearances to rally support.

Mr Ma, chairman of the Kuomintang (KMT) and favoured by Taiwan's business community, greeted shoppers at a night market in the streets of Taipei.

Ms Tsai, the Democratic Progressive Party (DPP) leader, visited the KMT strongholds of northern Taiwan. On Thursday a group of more than 200 academics threw their support behind her.

According to local media reports, Mr Soong, of the People First Party (PFP), is focusing the last leg of his campaign on Taichung, the third largest city on the island.

China Issue

About five to 10% of the voting population are more concerned about the economy and prosperity than ideological issues Dr Katherine Tseng, Research associate, East Asian Institute

Cross-straits relations with China, which still claims Taiwan as a province, and the economy are the key issues of the elections.

Mr Ma, who is seen as having improved ties with China, says a vote for him is a vote for peace.

His China-friendly approach has led to the establishment of regular direct flights and shipping links, as well as a landmark trade deal that cuts tariffs on hundreds of types of Taiwanese exports to mainland China.

But some voters are concerned that Mr Ma's policies will pave the way for unification with the mainland.

Ms Tsai's party favours Taiwan's formal independence from China. She has, however, made overtures to the mainland, saying that she is not against negotiating with China on economic and other matters as long as it does not affect Taiwan's sovereignty.

China nonetheless remains suspicious of her and her party. And while Washington has not openly endorsed Mr Ma, observers say it is an open secret that the US prefers his approach to China.

China is also entering a year of leadership transition as President Hu Jintao and other senior leaders are due retire. Mr Hu is expected to hand power over to Vice-President Xi Jinping at a Communist Party Congress later this year.

'Swing voters'

Taiwanese voters - even husbands and wives - are divided over which candidate is the best one to guide Taiwan The BBC's Cindy Sui in Taipei Taiwan braces for election battle

Observers say ''stability and prosperity'' issues are more likely to determine the outcome than ideology.

''About five to 10% of the voting population are more concerned about the economy and prosperity than ideological issues,'' said Dr Katherine Tseng, a research associate at the East Asian Institute in Singapore.

These potential ''swing voters'' include first-time voters who are educated and have more foreign experience, she added.

Whoever wins will have to steer a careful course on China.

Mr Ma could find himself caught between Beijing wanting to move faster on relations and opposition pressure at home, Dr Tseng said.

Ms Tsai, meanwhile, could face a ''cooling off period'' in ties with China - but the two would find a way to talk, she added.