It's confirmed, Dr Mahathir is backing Tengku Razaleigh Hamzah to become the next President of Umno in December (read here). It is also true that Dr Mahathir will re-join Umno for this purpose. The man credited for persuading the former PM to return to the party is Muhyiddin Yasin (read here).
On Saturday, Mukhriz confirmed that he will stand in the way of Khairy Jamaluddin's dream to be the Umno Youth chief (read here). Two others may enter the fray.