Ella Henderson has been predicted to claim the show's grand prize since she burst onto the show in the first auditions episode back in August.
However, following some criticism from the judges over a couple of Henderson's live show performances and a strong couple of weeks from 21-year-old Douglas, bookmakers have switched the odds.
The supermarket worker can now be backed at 11/8, ahead of Henderson at 7/4.
James Arthur is the third favourite (3/1), ahead of Christopher Maloney (12/1) and Union J (25/1). Rylan Clark is a massive longshot to win the whole series at 80/1.
Douglas's performance of Robbie Williams's 'Angels' won him massive praise from the judges on Saturday night.
Louis Walsh described Nicole Scherzinger's act as a "star in the making", while Gary Barlow described the singer as "absolutely incredible".
Watch Jahmene Douglas covering 'Angels':