China's dream of a strong, pro-unification political bloc emerging in Taiwan suffered a serious setback over the weekend when the island's influential former president signaled a break with his own party to support President Chen Shui-bian, who once advocated Taiwanese independence.

For months, the Chinese government has tried to isolate Chen by courting his rivals, and it has been counting on the opposition Nationalist and People First parties to strengthen their grip on Taiwan's parliament and oust Chen or force him to adopt more favorable policies toward the mainland.

But that strategy is in trouble now that former President Lee Teng-hui, who led the Nationalist Party for more than cade, has all but confirmed he will abandon the party and throw his support – and that of his many followers – behind Chen's Democratic Progressive Party during the legislative elections in December.

At a meeting of a pro-independence academic group on Saturday, Lee and Chen made their first joint public appearance since Chen took office. Lee delivered a speech calling for "the birth of a new Taiwan." Then, before a cheering crowd, the two men clasped their hands and raised them over their heads in a common Taiwanese campaign gesture.

The image was plastered on the front pages of several Taiwanese newspapers and shown repeatedly on the island's 24-hour cable news channels, and a possible "Lee-Bian" alliance is the talk of Taiwan now. "Political Focus Remains on Lee," read one large headline in Taipei today, while another writer described the development as "dazzling and dramatic."

Lee has declined to discuss his intentions, but he has endorsed two biographies published in Taiwan this month that make clear his disdain for Nationalist Party chief Lien Chan and People First leader James Soong. Chen wrote the preface for one of the books. In addition, a former cabinet member and Lee loyalist has been quoted telling reporters that several Nationalist lawmakers intend to quit and form a new political party with Lee.

Lee, 78, remains popular among many Taiwan residents, particularly ethnic Taiwanese in the island's south. His defection could reshape Taiwan's political landscape, strengthening Chen's embattled presidency and weakening the Nationalists, who ruled the island for more than 50 years before Chen was elected last year.

It could also further polarize public opinion in Taiwan over whether the democratic, self-governing island should move toward unification with or greater independence from China, which considers Taiwan part of its territory. Lee and Chen have advocated a go-slow approach to unification talks, while Lien and Soong have urged closer ties with Beijing.

"This is the beginning of an active political realignment in Taiwan, and this realignment will create more divergence between mainland factions and Taiwanese factions," said Andrew Yang, secretary-general of the Chinese Council of Advanced Policy Studies, a think tank in Taipei. "The process is a dangerous one, because it may induce Beijing to think it's impossible for them to take Taiwan back peacefully."

If China concludes its strategy to isolate Chen has failed and sees him gaining strength because of Lee's support, it may give up on a political solution and focus on its military options to recover the island, Yang said.

But he said China will probably wait for the results of the December elections before reevaluating its Taiwan strategy.