The master's thesis addresses the National Assembly elections in 2018, i.e. a period of early elections. The main aim of the thesis is to examine, whether the electoral campaign had influenced the voter behaviour in the official electoral campaign period and one month before the official start. For this purpose, a theoretical framework of voter behaviour and election campaign was developed in the master's thesis, which explains the periods of changes in the election campaign and of the behaviour of individuals during this campaign. Emphasis is placed on the explanation of voter behaviour in individuals; therefore, an overview is prepared of the development of different schools of voter behaviour as well as the meaning of short-term and long-term factors in the explanation thereof. On the other hand, emphasis is placed also on the election campaign and different channels or mechanisms for communication of candidates and political parties with the voters. A key chapter is the analysis of the actual connection between voter behaviour and electoral campaign. The analysis of this connection was made with the help of public opinion surveys, which demonstrate the changes in the run-up to the elections. In the final part, these changes are presented, and results are interpreted. In conclusion, our findings are presented. The exploratory question and hypothesis, which were raised in the introduction, are answered.