D.P.P.

D.P.P. supporters cite a clip of him in 2005, lashing out at opposing Nationalist Party members in the legislature for blocking a budget proposal to buy U.S. submarines, jets and missiles.

Ms. Tsai brought the D.P.P. back to power in 2016 after it had earlier suffered a devastating loss at the polls.

“Tsai Ing-wen joined the D.P.P. as an outsider, when the D.P.P. needed an outsider,” said Jou Yi-cheng, a former senior official with the party who got to know Mr. Lai when he was starting out in politics.

“But Lai Ching-te is different. He’s grown up within the D.P.P.”

“Lai Ching-te has come all the way from the grass roots — as a congress delegate, legislator, mayor, premier — climbing up step by step,” said Tseng Chun-jen, a longtime activist for the D.P.P. in Tainan.