It grew out of the Tangwai movement formed in the 1970s to oppose the ruling Kuomintang.
The Taiwan Solidarity Union (TSU) is a left-wing progressive party characterised primarily by its Taiwanese nationalism and derives its membership from both the Kuomintang's former moderate and Taiwan-oriented fringe and DPP supporters disgruntled by the party's moderation on the question of Taiwanese sovereignty.
Its progressive character is questionable, although it is part of the DPP's pro-Taiwan independence Pan-Green alliance.
The modern liberal parties in Taiwan are mostly associated with Taiwanese nationalism, as well as liberal positions on social issues, such as support for LGBT rights and abolishing the death penalty.
However, progressivism and social liberalism in Taiwan have not easily extended to extensive labor rights, or more liberal support for immigrant rights.