We can’t deny that kiai and santri have a long history in the dynamics of Indonesian politics. On the other hand, the number of Islamic boarding schools and students experienced a very significant development. So it is not surprising that Islamic boarding schools will become the target of election participants (legislative candidates) to gain votes, especially Islamic boarding schools which have a large number of students. This study was aimed to explain; 1) How Kiai’s voting behavior during the 2019 Legislative Elections; 2) How was the voting behaviour of Santri in the 2019 Legislative Elections; and 3) How Kiai influenced the voting behaviour of Santri in the 2019 Legislative Elections. The method used in this study is descriptive qualitative by observing the case study at the Wisma Wisnu Islamic Boarding School, Madiun. The data was analysed by using sociological theory (The Columbia Study) and Rational Choice. Moreover, the findings of this study showed that: 1) the voting behaviour of Kiai in the 2019 Legislative Elections showed rational choice, Kiai was able to assess the quality, competence, and the integrity of the legislative candidates through vision, mission, and their programs. 2) The voting behaviour of Santri in the 2019 Legislative Elections showed sociological approach (The Colombia Study), they did not know the vision, mission, and programs brought by the election candidates because they were not involved during the campaign stage. However, the Santri only considered and made their choice based on their Kiai’s guidance and their parents as well; 3) The sacred and tendentious relationship between Kiai and Santri was used by Kiai to influence santri’s behaviour in the 2019 Legislative Elections.