Treballs finals del Màster en Análisi Política i Assessoria Institucional, Facultat de Dret, Universitat de Barcelona. Curs: 2017-2018. Tutor: Albert FalcoPartisanship theory states that there is a relationship between election results and policy outcome; therefore, a government elected will represent its policy standings and act on its implementation during the mandate. By relying on assumptions from partisanship theory, I am testing how government formation impacts the votes cast toward radical parties by looking at data from many European countries. More particularly, this study will show how the position of a government on the left-right scale affects the emergence or the success of radical parties. The argument that the likelihood for the emergence or success of radical parties of the same color as the incumbent is lower has been tested in 15 European countries from 2002 to 2015. To test the argument, I used linear and logistic regression techniques, which showed that the likelihood for a far-right party to emerge or succeed when a right-leaning government formation is the incumbent decreases when the analysis is done over all countries under study as well when done individually in Denmark and in the region of Catalonia, while the likelihood for a far-left party to emerge or succeed under the same conditions, increases in only a few cases. The analysis shows mixed results on the impact of government formation on votes cast for radical parties.