Contemporary political science research has shown that magnitude, i.e., the number of seats at stake per constituency, is the single most important factor regardless of type of electoral system. Recent French electoral reforms applied to the 2004 European elections provide an interesting case through which to assess this claim and to test its validity. Since the reform only changed one rule, namely magnitude, the main goal of this paper is to test the temporal and spatial impacts of this reform on the results. First, we compare the 2004 results with those of previous European elections in which magnitude was higher. Second, we conduct a constituency-level analysis of the 2004 European elections results since the number of seats at stake differs according to constituency. Finally, the study confirms the effect of magnitude on the party system. More specifically, it shows both its mechanical effects on parliamentary representation and its psychological effects on voters.