Modern democracy works with party politics because democracy involves the active participation of political parties for its sustenance. Therefore, Political parties, as democratic institutions are expected to be the carriers of democratic principles through which democracy can be properly actualized. Hence, a critical analysis of political parties revealed that they are crucial tools for promoting democracy. The quest to wrestle power from the PDP which has ruled Nigeria since the return to democratic rule prompted the then three main opposition parties; ACN, ANNP, CPC, and a faction of APGA to merge and form a mega opposition party called the All Progressives Congress (APC) on February 6, 2013. This paper attempts an analysis of the politics of party merger and lack of internal democracy in the ruling APC and its implications on democratic consolidation in Nigeria. It employed the Heuristic theory of party merger as a framework of analysis while adopting the qualitative research method with reliance on the secondary sources of data. The findings revealed that the inability of the APC National Working Committee and executive branch to harmonize divergent interests of members by allowing a level playing field for all party members resulted to intra-party conflict, fractionalization and defection of some members to other platforms. It concluded that this lack or absence of internal democracy in the APC does not only challenge the credibility of the electoral process but also makes the entire process undemocratic. The paper recommended among other things the entrenchment of internal party democracy within the internal structures and dynamics of the APC particularly in the selection of candidates for elective offices and political positions. Keywords: Politics, Party merger, Internal Democracy, APC, and Intra-party conflict..