Ladbrokes have stopped taking bets on his cover of Mariah Carey and Whitney Houston's 'When You Believe' taking the coveted title.
"Leon is practically guaranteed top spot," said company spokesman Nick Weinberg. "It will be a massive surprise if he doesn’t record the festive chart topper.
“The X Factor winner and Christmas number one go hand in hand."
A spokesman for HMV said Jackson could shift 400,000 copies of the single in a matter of days. Last year's winner Leona Lewis sold some 500,000 of her victory release in less than a week.
"You have a very motivated fan base who have been watching X Factor," he explained. "Millions of people will have voted last night."
> Welsh radio stations ban 'When You Believe'