The reality is, Oğan ran with the weight of Zafer Partisi behind him. Nobody was speaking about Oğan a few months ago just before he was announced as a candidate. All the work to garner attention and bring a more nationalist candidate to the election was done by Ümit Özdağ, the founder of Zafer Partisi. His first choice to be a candidate was Mansur Yavaş, the current mayor of Ankara. Oğan wasn't even his second candidate of choice; it was Muharrem İnce, but he threw a hissy fit and decided to run by himself. Özdağ will now more than likely back Kılıçdaroğlu, which is exactly what the opposition needed, as Özdağ's reputation as the central nationalist will bring votes he desperately needed to even have any chance in the second round. Furthermore, this might finally push İnce to back Kılıçdaroğlu, which would act as further proof to the nationalists that he's an acceptable candidate.
My current guess is, the incumbent president does have enough to get over the line, especially with a few cards up his sleeve, but what Oğan brings to the table won't give him anything resembling a commanding lead. If anything, Oğan has badly overestimated his appeal.