The plurality vote (first-past-the-post) is one of the most restrictive electoral systems used for parliamentary elections. Empirically, its deterring effect on small political parties has been widely studied at the national level, while theoretical arguments highlight its strategic effect at the district level. This paper argues that the strategic effect, reducing the votes expressed for minor parties in plurality vote systems, is uneven across districts. The strongest strategic effect is expected in very competitive constituencies, where the two strongest candidates are in close competition with each other. The paper estimates the effect empirically, based on electoral results for minor political parties from six parliamentary democracies using the plurality vote. The methodology proposed in this paper allows me to separate sociological or geographical factors from strategic factors affecting party support. Results show that due to the strategic effect, minor parties lose some 15% of their votes in very competitive districts.