Studien avser att förklara riksdagspartiernas inställning mot Natomedlemskap över tid. Därför utförs en policyanalys inom ramen för ''The Advocacy Coalition Framework'’. Detta genomförs genom att kategorisera riksdagspartierna till relevanta advocacy coalitions utifrån deras beliefs. Studien använder sig av utrikespolitiska debatter för att avgöra respektive riksdagspartis beliefs. Genom att undersöka riksdagspartiernas normative och empirical policy core beliefs över tid kan studien finna likheter och skillnader mellan advocacy coalitions. Vad studien kommer fram till är hur riksdagspartierna tar en annan ställning inom säkerhetspolitiken och hur gemensamma beliefs kan förekomma mellan advocacy coalitions. Med åren går det även att se hur riksdagspartier börjar värna mer om militära medel för svensk säkerhet. Studien erbjuder också ett teoretiskt intressant inlägg genom att lyfta upp hur empirical policy core beliefs binder också advocacy coalitions varifrån tidigare forskning visar hur oftast normative policy core beliefs avgör strukturen i advocacy coalitions. Riksdagspartiers ställningstagande antingen för Natomedlemskap eller mot Natomedlemskap blev relevant för vilken advocacy coalition riksdagspartierna blev kategoriserade inom.

This thesis investigates the circumstances under which parties change their positions, with Swedish nuclear power policy as a case to adress the purpose. The thesis employed qualitative text analysis and the theoretical framework Advocacy Coalition Framework (ACF) to examine and adress the the thesis's research questions and purpose. ACF was used to formulate the research questions, focusing on wether there had been changes in the Swedish parliamentary parties' policy core belifes regardning nuclear power policy and, if so, wether external subsystem events and or\changes in coalition formation could explain these changes. The study found that three out of eight Swedish parliamentary parties had changed their policy core belifes regarding the nuclear power issue:the Social Democrats, the Green Party, and the Center party.  At least one of the examined external subsystem events could either explain the changes or reinforce previous changes. Furthermore, the sudy showed that changes in coalition formation could potentially explain the Social Democrats' and the Green Party's altered policy core belifes. Other potential explanations included the influence of the Janaury Agreement, where the Liberals, as a strongly pro-nuclear party, may have influenced the Green party and the Social Democrats to become more positive towards nuclear power. In summary, the sudy demonstrated that changes in coalition formation and\or external subsystem evenets are circumstances that can explain why parties change their positions. Additionally, the thesis suggested that ACF should include two additional external subsystem events, which this sudy has shown to have an impact on parties' changed policy core belifes:war and economic changes.