TAIPEI, Taiwan -- TAIPEI, Taiwan (AP) — Taiwan investigators were expected to rule Sunday on the further detention of a former presidential candidate amid graft allegations that have sparked minor street protests by his supporters.

Ko Wen-je, leader of the Taiwan People’s Party, was detained overnight and has a hearing scheduled for Sunday. His supporters gathered outside the prosecutor's office in Taipei, holding signs and chanting slogans demanding Ko's release and denouncing what they perceive as judicial injustice. Investigators declined Ko's request to return home, citing concerns about potential collusion with others involved in the case.

Ko, a physician by training who previously served as mayor of Taipei, and his TPP emerged as a third force in Taiwan's often lively democracy. This political landscape is typically dominated by the ruling Democratic Progressive Party and the remaining members of the Nationalist Party, which fled to Taiwan after the Communist Party seized control of mainland China in 1949.

Ko and others were implicated in May in a scandal involving the developer of the downtown Core Pacific Center shopping mall. During Ko's 2014-2022 tenure as mayor, the developer was granted permission to significantly expand the mall's rentable floor space. Authorities raided Ko's home and TPP offices prior to his questioning on Friday. The shopping center is still under construction, and DPP politicians have called for a halt to construction or even demolition.

Ko finished third in this year's election with roughly a quarter of the vote. The DPP's William Lai Ching-te emerged victorious, and his party advocates for continued de facto independence from China. The TPP secured just under 3% of the seats in the legislature.

Ko gained notable support among young voters despite lacking a clear political agenda. He briefly considered alliances with both the DPP and Nationalists but failed to reach an agreement, leaving him with limited political allies beyond his own supporters.

Previously a significant issue, political corruption has experienced a decline in public concern as independent investigators have gained more authority.