The threat of a split, however, has been there since Hsieh lost his presidential bid last year.

Hsieh, a Taipei-born former premier, announced that he was quitting politics when he conceded defeat to his rival Ma Ying-jeou on March 22, 2008.

But Hsieh remained acting DPP chairman until Tsai Ing-wen was elected and took over from him. He has never given up on politics, instead harboring hopes of forming a new party of his own.

Aside from taking part in every DPP rally, Hsieh kicked off a radio political forum toward the end of last year. The program is aired every Wednesday by the Green Peace Broadcasting Station in Sanchong, a city opposite Taipei across the Tamsui River.

On May 19, Hsieh called a meeting of his political talk show fans, where he announced the inauguration of a Taiwan Zhang-gong National Salvation Army.

Zhang-gong has a double meaning. In the past, it meant indenture. Zhang, which means long, is also the first character of Hsieh's Chinese given name, which is Zhang-ting. Gong means work. Together, Zhang-gong means long (voluntary) work for Frank Hsieh.

The announcement came a little more than one day after Tsai Ying-wen's mass rally on May 17 and the following 24-hour sit-in to protest against President Ma Ying-jeou's supposed sellout of Taiwan.

In an opening statement at the inauguration of his volunteer army, Hsieh said the DPP will be forsaken and taken over by "a new power," if it goes against the wishes of the people.

"Before that new power becomes strong," Hsieh went on, "we have to take part in DPP activities and accept the party's leadership."

But, Hsieh pointed out, "when the new power takes the lead in the future, the Democratic Progressive Party has to accept and obey the new power's leadership."

By new power, it is widely believed that Hsieh is referring to a new party of his own.

Asked whether his political move runs counter to his vow of retirement from politics, Hsieh replied he announced an end of his political career, not the end of "being a Taiwan citizen."

That means he can continue discharging duties as a responsible citizen of Taiwan, including the formation of a new party and carry its standard in the 2012 presidential election.

According to Chao Tien-ling, Hsieh's top aide who heads the DPP youth department, the ex-premier has "an excellent grasp" of Taiwan's political trend.

"He knows Ma knows our native-born islanders are very contentious," Chao says. "It's our bondage of fate not to be able to stand united. If the DPP is split, the only one to benefit is Ma Ying-jeou."

Chao quotes Hsieh as demanding the opposition party's solidarity. Hsieh doesn't want to split the party, now that Tsai has mended fences with all her opponents within the party after presenting a united front in leading at least 200,000 supporters in a Taipei rally on May 17.

The situation may change, depending on how the opposition party fares in the year-end local elections.