ANKARA, Turkey (AP) — A university invalidated the diploma of Istanbul Mayor Ekrem Imamoglu on Tuesday, in a move widely perceived as politically motivated to block the popular opposition figure and President Recep Tayyip Erdogan's key rival from running in the next presidential race. Istanbul University nullified Imamoglu’s diploma, citing alleged irregularities in his 1990 transfer from a private university in northern Cyprus to its Faculty of Business Administration. The decision disqualifies Imamoglu from running for president — a position that requires candidates to hold a university degree.