一國的對外關係會不會影響國內的政治局勢？學界對此一問題的答案是肯定的。重點是在於會在什麼樣的情況下以何種方式影響？本文採取了選票極大化模式來檢視中華民國(2000)、南韓(2002)與烏克蘭(1999)三國最近的一次總統選舉。上述三國都有一個特殊的「對外政策」(兩岸關係、兩韓關係與俄羅斯／烏克蘭關係)主導了選民的認同與投票傾向，而且從歷屆總統選舉中呈現出民意集中在對外政策立場上的中點。本文在比較了三國總統選舉的過程後發現，在一個以認同政治為主，關鍵議題上民意呈常態分佈(也就是民意的重數在中)的國家，趨中的民意會誘使各政治勢力將其立場往中間靠攏。台灣的陳水扁，南韓的盧武炫與烏克蘭的庫奇馬更是在競選過程中將上述的特徵清楚地表現出來。 / Does a country’s foreign relation have it’s impact on domestic politics? Academic research has already answered it, the point is when and how. The major purpose of this thesis is to use vote-maximizing model to examine the presidential elections of the ROC (Taiwan) in 2000, South Korea in 2002 and Ukraine in 1999. All these countries have a kind of special “foreign relation” with them; cross-Strait relations for Taiwan, Inter-Korea relations for South Korea and Russo-Ukrainian relations for Ukraine. Besides, such the relation has the main feature of leading one country’s nature of elections and people’s identity. Evidence also shows there is a standard distribution of public preferences on mixed identity. After comparing the three elections, our finding is: if a country’s salient issue lies on identity politics, and public preference is concentrated in the middle, than public preference will induce political parties (or electoral candidate) to move ideologically toward the center. Chen Shui-Bian in Taiwan, Roh Moo Hyun in South Korea and Leonid Kuchma clearly demonstrated the above feature in their electoral strategy.