The purpose of this essay is to analyze why the Sweden Democrats (SD) continued to grow in the 2018 election, while the Danish Peoples Party (DF) lost over half of their support in the election in 2019. By using a structured, focused comparative method, the essay analyses the similar political systems of Denmark and Sweden, focusing on the traditional established parties’ different strategies to gain back the voters lost to populists. The analysis concludes that the success of SD and failure of DF can be contributed to ineffective strategies by Sweden’s traditional parties and a more effective strategy in the Danish case. Sweden’s established parties used isolating strategies by demonizing SD and their voters as extremists, paving way for SD to use populist political communication. In the danish case, most established parties have legitimized DF by co-opting their stances on immigration. The blue block has cooperated with DF in the Danish government.  By anchoring the analysis in theories about favorable conditions for populism, the main conclusion is that SD, because of the established parties’ isolating strategies, have been able to use populist political communication to present themselves as a distinct political alternative which mobilizes voters. DF have not had this opportunity, due to the co-optation, cooperation and broad consensus on their main issues