近年來，臺灣許多政治人物在公開場合發表談話中常將國語、臺語交互使用，這種將不同語言互用的現象，在語言學上稱為「符碼轉換」(codeswitching)。過往的研究顯示，「符碼轉換」為一重要溝通策略(conversational strategy)，多出現在所使用之主要語言缺乏適當表達之詞彙；為充分表達內容之透切性及加強重複表達語氣時候，具有發揮談話策略運用之功能。另一方面，若是夾用較弱勢語言談話，則可爭取弱勢族群認同或表達說話者親切度與幽默感等。然而過往之研究範圍僅限於一般會話、書面文件或報紙標語，對於目前臺灣政治人物交錯使用政治性談話雙語策略並無系統之研究。 本文主要採用質化研究方法及文獻分析，同時論證陳總統之轉換使用語，一方面可有效運作為講話策略工具，並展現經由語言轉換使得政治性談話具有溝通技巧，加深選民認同感及族群意識。另一方面也有可能產生加深族群間的藩籬、暗批對手或諷刺時政。

　　　　　In this paper, I extend the study of codeswitching to the ever important, though oft neglected area of political discourse. I cite instances of Taiwanese president Chen Shui-bian.s codeswitching between Mandarin and Taiwanese in the 2001 legislative and city magistrate election, and I argue that this codeswitching is adopted as a conversational strategy for both pragmatic and strategic purposes. I demonstrate that codeswitching in political discourse is an interpersonal strategy that can be used to create, strengthen, or destroy interpersonal boundaries. In addition, it can also be used as a symbolic practice for practical and political purposes. I adopt Rational Choice Models(RC) (e.g., Myers-Scotton 1993, Myers-Scotton and Agnes Bolonyai 2001) for analysis of codeswitching in political discourse; and I contend that,though most instances of codeswitching will reflect conventional expectations of language choice to a certain extent, speakers make rational individual choices. This is especially evident in political discourse, where a politician can rely on the ambiguities of the inference of a language choice to avoid alleged responsibility, redefine interpersonal boundaries, or take refuge in a different role. In short, a rational-based choice-model helps explain how a politician can use an array of language choices to maximize his personal/political gains and minimize personal/political risks. It is further suggested that the inference of a codeswitch is indeterminate and ambiguous (Heller 1988). The ambiguity and indeterminacy of a code choice are especially important in political discourse where conflicts and confrontations are common and where indirectness and involvement are necessary. Thus, studying codeswitching in political discourse will, on the one hand, enhance our understanding of codeswitching in general from a specific genre, and, on the other hand, will also add to our appreciation of political discourse from a more specific sociolinguistic perspective.