In his victory speech, Chen rejected China's "one country, two systems" formula for reunification by stating that Taiwan's sovereignty must be protected. He also invited the PRC's leadership to engage in a dialogue with him to resolve the future of Taiwan-China relations. On taking office, Chen faced major leadership challenges. For the past half-century, the KMT had controlled national politics and the stability that it brought could no longer be taken for granted. Further complicating the political environment was the KMT control over Taipei and the Legislative Yuan. Chen's China policy has shifted considerably during his term in office, and remains his biggest challenge, as his pro-independence views are balanced against real threats or promises from the Mainland.