The People’s Democratic Party (PDP), the dominant party in Nigeria’s Fourth Republic since inauguration of the Republic in 1999, found itself out of power and in opposition following its unprecedented defeat in the 2015 presidential and other elections. This chapter examines the background, historical context, nature, and matters arising from this transition of the PDP from ruling to opposition party. It shows how the transition was signposted by a decline in party vision, structure, coherence, performance, and reputation complemented by a gradual consolidation of opposition parties and interests into a single formidable platform, the All Progressives Congress (APC), which successfully wrested power from the PDP in 2015. The chapter demonstrates that impunity embedded in antidemocratic schemes that make party and electoral rules subject to pro-power interpretations while making outcomes predictably pro-dominant power provide only a fragile basis for party rule.