台灣的統獨立場看來接近常態分佈，但爲什麼政黨的意識型態趨向兩極化？本論文主張，所謂的常態分佈，建立在單維空間的假定上，而部份「偏好不可分離」（non-separable preferences)的選民經常選擇「維持現狀」，留下常態分佈的印象。一些文獻已經發現，某些人的統 獨立場具有條件性，但對於這些條件從何而来，仍有探索的空間。本 文認爲，條件式立場和論述所傳遞的訊息有關，而中國國民黨既然具有詮釋兩岸關係的優勢，又從2008年執政迄今，比較容易操作相關訊 息並影響投票抉擇。若然，在2012年總統選舉投給馬英九的選票，部 分應該來自支持條件式統一的獨派選民。本文以社會變遷調査爲檢證 這個假設的資料，主因在於統獨選擇和理性判斷與情感認同有關，而 該資料庫詢問了許多相關的問題。結果發現，這些支持條件式統一的 獨派選民的確增加了馬英九的選票，而他們在同時舉行的單一席次區 域立委選舉中，投票給國民黨候選人的比例明顯低於投票給馬英九的 比例，顯現此類選民的投票抉擇受到兩岸關係論述的影響。本文也發 現，在支持條件式統一的獨派選民中，與中國大陸的經濟互動的確增 加了投票給馬英九的機率，但對於偏獨且不支持條件式統一的選民，若 以台灣爲祖國且對台灣民主政治具有光榮感，仍然不太會投票給馬英九。

Why are Taiwan’s political parties taking polarized positions on the unification-independence issue even though the voters’ attitudes appear to be a normal distribution? This paper argues that this impression results from a presumption of uni-dimensionality. Although some studies have found the existence of conditional alternatives for the choice of Taiwan’s unification or independence, the sources of these conditions remain unspecified. This paper shows that conditional preferences are shaped by information associated with a discourse. The Kuomintang (KMT), Taiwan’s ruling party since 2008, has an advantage to manipulate cross-strait information and affect vote choice. If this theory holds, the victory of Ma Ying-jeou, the KMT’s candidate in the 2012 presidential election, should had been affected by the pro-independence voters who could conditionally endorse unification. To test this hypothesis, this paper uses the Taiwan Social change Survey to study how the choice of Taiwan’s unification or independence has been constrained by the rational and emotional factors, about which the dataset contains many related questions. The major finding is that the pro-independence voters who may conditionally endorse unification have indeed increased Ma’s vote share. These voters are less likely to vote for the KMT’s legislative candidates elected under the same electoral system, a gap demonstrating the impact of cross-strait discourses on their vote choices. Lastly, this paper shows that the probability of a conditional pro-independence voter voting for Ma increases with his/her involvement in the cross-strait economic exchanges. But for pro-independence voters who do not endorse reunification, treating Taiwan as their motherland and feeling proud of Taiwan democracy will decrease their chances of voting for Ma.