Questions about the legitimacy of Turkish President Recep Tayyip Erdogan's university diploma have been simmering for a while and now have the potential to become a major issue.

Erdogan went to an imam-hatip school, a high school-level institution that educates religious preachers. During the 1970s and 1980s, graduates of those schools could pursue their higher education only in theology. Erdogan, however, was thought to have graduated from Marmara University’s Faculty of Economics and Administrative Sciences; to have registered there, he would have needed a certificate to prove he was also educated at a school other than an imam-hatip school.

There starts the scrutiny of Erdogan's diplomas, or rather, whether he has valid documents to prove he is eligible to be president.

The latest allegation is that he doesn't have a valid university diploma. If true, it would have enormous consequences because, according to the Turkish Constitution, the president should be an alumnus of a university or an institution of higher education. The constitution's Article 101 stipulates that and it is unequivocal.