瑞典民主黨
Karlsson first joined the Sweden Democrats in 1994, which was then led by Anders Klarström. His first important impact within the Sweden Democrats came in 2002, when he alongside Jimmie Åkesson and former leader Mikael Jansson reshaped the party's political programme. According to "Expo", Karlsson also wrote the Sweden Democrats' election manifesto for to the 2006 general election. Since 2008, he is recognized as the leading ideologue of the Sweden Democrats, after its former chief ideologue Johan Rinderheim was forced to leave the party.