Taiwan opposition Democratic Progressive Party (DPP) chairwoman Tsai Ing-wen registered on Sunday morning as a candidate in the party primary for Taiwan's leadership election next year.

Tsai is the only DPP member in the running for the election, as Tainan Mayor William Lai and former DPP chairman Su Tseng-chang, both previously considered to be challengers, have decided not to run.

It will be the second attempt by Tsai, 59, to win the leadership election after she lost to incumbent leader Ma Ying-jeou of the Kuomintang (KMT) in the 2012 race.

Formerly a university law professor, Tsai joined the DPP in 2004 and was elected legislator.

Tsai was first elected DPP chairwoman in 2008, becoming the first female chairperson among Taiwan's major political parties. She was re-elected twice as DPP chairperson in 2010 and 2014.

Tsai served as Taiwan's mainland affairs chief from 2000-2004 when Chen Shui-bian was leader and assumed the post of deputy chief administrator in 2006-2007.

The DPP began its candidate nominating process for the election on Thursday last week. Those who want to register for the party primary can apply until Feb. 16.

The ruling Kuomintang (KMT) has not yet started its nomination process.