I explore a developing dimension of party strategy, known as the issue diversity dimension, in three major sections across three different cases. First, I conceptualize and formalize a measure to measure the issue diversity dimension and its impact across mainstream and niche parties (chapter 2). I follow with a quantitative case study of the United Kingdom to determine the exact relationships between the issue diversity dimension and electoral success (chapter 3). Second, I conceptualize the potential impact of the issue diversity dimension on Japanese parties (chapter 4). I follow with a quantitative case study of how issue diversity impacts the electoral outcomes of Japanese parties (chapter 5). Third, I conceptualize the potential impact of the issue diversity dimension on the electoral success associated with radical right populist parties (chapter 6). I follow with a quantitative case study of radical right populist parties spanning several western European democracies to determine when they experience electoral success (chapter 7). Finally, I conclude with a discussion of the findings, implications, and directions for future research.