Elections are in fact specific mechanisms for aggregating political preferences of the majority of voters into one will, transforming votes into seats. This is the major role of any election, whether at local, parliamentary, or EU level. The elections of the members of the European Parliament by direct and universal suffrage started in 1979, with the proposal that the members of the EP to be elected in accordance with a uniform procedure in all EU countries. In pursuit of a uniform electoral procedure for all the member-countries meant that European elections must be based on the principle of proportional representation using either the list system or the STV system. However, it turned out, that some challenges and difficulties arose reaching agreement on common principles of all countries and on the harmonisation of national traditions. One of the consequences of the complex relationship between the national parliamentary and the EP elections is that the composition of the EP does not precisely reflect the actual balance of political forces in the European Community, because the national political systems actually decide most of what there is to be decided politically. The European elections turned out to be second-order elections as additional political events to national elections. The most important political issues thus are determined more by the domestic political cleavages, than by decisions originating in the European Community. The present paper analyses the interrelationship between the first-order national elections and the second-order European elections based more or less on the works of Reif–Schmitt (1980), Marsch (1998), Covař (2016) and others.