Argument: Turkey size would give it too much voting power in the EU
"Turkey’s Membership Application: Implications for the EU". Jean Monnet/Robert Schuman Paper Series. Vol. 5 No. 26. August 2005 - "The nature of the threat that Turkey is widely held to pose is seen as taking different forms. For example, Turkish accession clearly will impact on EU institutions and decision making processes. The Commission will perhaps not be overly affected, but existing member states’ presence in the Council and the EP most certainly will be, with larger and medium-sized states in particular losing presence and voting strengths."