從理性抉擇途徑探討民眾的政治態度或行為，議題立場無疑是一項重要的解釋變數，但過去研究卻都忽略了，民眾對議題的重要性認知可能存在的中介影響效果。本文假設，當民眾認為該議題相對重要時，較容易確立自己及政黨在該議題上的位置，同時拉大主要政黨的立場差距，進而影響其政治態度的形塑。對此，本文利用民意調查資料，探詢台灣民眾對「兩岸統獨」及「核能發電」兩項議題重要性認知的影響，並檢證其對形塑政府施政評價的中介效果。整體而言，本文資料分析的結果支持前述假設。不過，假設成立與否，仍須視議題屬性而定，當議題屬於長期僵化且難以解決時，將會削弱議題重要性對政治態度形塑的中介影響力。

Issue position is undoubtedly an important factor in accounting for individuals’ political attitudes and behaviors from the approach of rational choice. But the possibility that the perception of issue salience plays a moderating variable has been neglected in the literature. It is hypothesized in this study that people are more likely to be aware of their and the parties’ positions on a particular issue when they consider the issue important. Meanwhile, people tend to exaggerate the distance between major parties’ positions on such an issue. People’s perception of issue salience, therefore, shapes their political attitudes. Survey data are used in this study to analyze people’s perception of salience regarding “unification-independent “and “nuclear power” in order to examine their hypothesized role of moderating variables shaping people’s evaluation of government performance. It is found that the results of data analysis support the above hypotheses. However, such results depend on the nature of the issues. If people hold rigid attitudes toward an issue over the long term, its moderating effects on shaping people’s political attitudes are reduced.