This dissertation addresses two important questions: what constitutes regionalist party success and what factors explain this success? Regionalist parties are political parties that compete within a confined geographic region and focus on gaining greater political autonomy. This differentiates them from mainstream parties who prefer to emphasize traditional left-right political issues and compete across the entire country. I argue that to better understand the electoral outcomes of these parties, their results need a more nuanced categorization: breakthrough, failure, and persistence. Breakthrough occurs when a party has a large surge in support. Electoral failure happens when a party suffers a precipitous decline in vote shares, diminishing its political relevance. Persistence results when a party replicates its previous electoral outcome with minimal change. I used a supply-side and demand-side theoretical framing to consider the influences on regionalist party outcomes. Demand-side or “bottom-up” based theories state that political parties are primarily responsive organizations that adapt to changes in public attitudes. Thus, they must respond and closely align with the social, cultural, and economic positions of the public. I hypothesized, however, that supply-side factors best explain a regionalist party’s fate. Supply-side or “top-down” theories maintain factors outside of public demand can shape elections. These include institutional arrangements and party strategies, such as the positions the parties take and salience they give to particular issues. In this framework, the choices parties make can impact citizens’ voting. To explain breakthrough, failure, and persistence, I found three factors most relevant: the emphasis mainstream parties put on issues related to regional autonomy compared to left-right issues, the positions mainstream parties take on decentralizing power, and the positions that regionalist parties adopt regarding regional autonomy. When all of these align favorably in an election a party is more likely to breakthrough. In instances where all of them align unfavorably the probability of failure increases. Persistence is most probable when one or two of the factors is beneficial, but not all of them. I analyzed these questions using a mixed-methods approach that included multiple regression analyses and case studies of eight different elections in Scotland.

The main purpose of this essay was to study whether niche parties that were represented in municipal councils in Sweden during the 2007-2010 term of office were politically relevant. Furthermore, factors that might facilitate political relevance for niche parties were studied. Political relevance was studied using two theoretical perspectives. The objective model of political relevance presents four categories of relevance based on the relations between political parties in a political assembly; governing parties, coalition parties, blackmail parties and isolated parties. The subjective model of political relevance relies on the party representatives’ own judgments of the relevance of their parties. To study objective and subjective political relevance, party representatives were interviewed. The results showed that seven out of eight niche parties were politically relevant according to the objective model, and six out of eight niche parties were relevant according to the subjective model. For the study of possible facilitating factors, a comparative table was formed using statistics and official data. Percentage of seats and type of majority coalition seemed to affect the possibilities for niche parties to become governing parties. A large percentage of seats and being represented on the municipal executive board and committees seemed to facilitate subjective political relevance.