The doctoral dissertation deals with research into the effects of personalization of the electoral system primarily on political parties and candidates for deputies. The personalization of the electoral system means the introduction of mechanisms in the electoral system that ensure a greater role for voters in the election of their parliamentary representatives. I define the electoral system as a “set of laws and party rules governing electoral competition between and within the parties” (Cox 1997: 38). This wider definition of the electoral system gives us space to build a more complete picture of the electoral system’s impact on political parties, candidates and voters as main actors in the electoral process. The focus of the research is the relationship between personal and party representation. In order to conduct a more comprehensive analysis of the effects of personalization on political parties, the research framework is narrowed down to list proportional electoral systems with preferential voting. Contemporary liberal democracy is characterized by a highly personalized politics. Governments are more recognizable by their leaders than by the parties that are the basis of their constitution. This personalization trend is not characteristic exclusively of presidential systems, but has become a feature of parliamentary political systems. In addition to personalization of the party at the leader level, there is also the personalization of politics at the level of members of parliament (MPs). In this paper, we only use the term ‘personalization of a party’ in reference to personalization at the level of the MP. We will not deal with the question of the presidentialization of political parties. Under the personalization of a political party at the level of MPs, we mean strengthening the position of deputies in the intra-party decision-making process. Thanks to the introduction of preferential voting in list proportional list systems, the group of electoral systems in which voters play an important role in the selection of their representatives has significantly expanded. Historically speaking, the representative position has been strengthened by the accepted attitude that the MP, not the party, is the ‘owner of the mandate’; preferential voting supports this. This paper deals with the personalization of politics at the level of the representative—the political party. That is to say, it explores the question of to what degree personalization of the electoral system affects the political party, its intra- and its inter-party dimension. Moreover, the paper deals with personal and party representation, an area that is a new field of interest for political scientists. Through this relationship, I explore the effect of electoral systems on political parties, candidates and voters. in developing this work, I was guided by the results achieved by Katz (1980, 1986) and Marsh 9 (1985) who first dealt with this issue. In his book A Theory of Parties and Electoral Systems (1980), Katz took his first steps in the research of preferential systems. Five years later, Marsh (1985) was dealing with differences between the preferential systems in Europe. In their works, Katz and Marsh set forth the first hypotheses about the effects of preferential voting. Although there has been a growing interest in research in this area over the last decade, no significant progress has yet been made. Karvonen (2004) made a significant step in systematizing the hypotheses of Katz and Marsh, and he added some more points. In his last paper on this subject (2011), Karvonen was working within the same group of hypotheses, which were open to further research. They are the basis of this research, with additional contributions. A major impetus for this work was one of the most influential articles in this field, ‘Incentives to Cultivate a Personal Vote: A Rank Ordering of Electoral Formulas’ by Carey and Shugart (1995), which examines the question of the influence of electoral systems on the candidate’s electoral strategies—that is, how electoral systems influence the pre-election roles of parties and their candidates. The authors developed three variables: (1) lack of party leadership control over access to and rank in ballots; (2) degree to which candidates are elected on individual votes independent of copartisans; and (3) whether voters cast a single intra-party vote instead of multiple votes or a party-level vote. By combining these three variables, there are up to thirteen combinations. This approach set me up to explore the impact that personalization creates when it comes to the relationship between the MP candidate and the party, or the MP and the party. Most authors agree that the introduction of personalization of the electoral system significantly affects interparty relations, which are sometimes reflected in a high degree of autonomy in campaigning and even in the collection and spending of funds for funding of their personal campaign. The bidding of candidates from the same party exercises a strong influence on intra-party relations, and it often happens that rival relations within the parties remain in the shadow of rival relations between the parties.