本文旨在探討七十八年台北市南區立法委員選舉中，選民所處的社會網路對於投票選擇的影響。作者認為，若依照選民的社會網路位置加以分類，有助於我們從另一角度了解選民的政治參與以及政治態度。因此，本文依照台北市南區選民是否有受到他人動員將選民分成動員者、不被動員者以及被動員者。本文發現這三種選民在人口特徵上並無差異，但是在社會態度上有積極參與以及消極參與之分別。進一步分析選民的政治參與政黨選擇，我們發現動員型選民的政治參與程度最高，不被動員型最低，而動員型選民較偏好國民黨，被動員型較喜歡民進黨，不被動員型則意向不明。由此可知，在這一群選民之中存在一種垂直的社會網路。 根據以上的分析，本文對於台北市南區近年來的政黨體系變遷進行初步的探討。由於有一大部份的選民並沒有強烈的政黨認同，他們的政治資訊又少，因此他們有可能被政治菁英以及相應的政治議題所吸引，改變其投票選擇對象。

This article attempts to show that the social factor: the effect of social network is discernible and important in the 1989 Legislative Yuan election of Taipei City South district. Traditionally, analysis of Taiwanese voting behavior focused on the psychological factor. Party identification which shed light on the stability of voting behavior was often highly emphasized. By inspecting the interviweds' frequency of contacting and discussing with their friends or neighbors, it is ident-ified three locations in the social network. In the analysis of electorate's demographic characteristics and their political involve-ment as well as knowledge. It is found that a vertical association of mobilization exists between the three locations. Party identification dominates in the process of vote desicion, however, the vertical associ-ation help determine the formation of party preference. This paper explains how the social network influence the elector-ate, by observing the party preference volatility in the Taipei City South District. It is concluded that a part of electorate, who has not strong party preference, is changing their preference while old social network was replacing by new media and taking over by astute elite.