Bookmakers have taken a last-minute surge of bets on Jason to win Big Brother.
While Nadia remains favourite for tonight’s final, Jason’s odds are shortening all the time.
He looks set to finish way ahead of fellow finalists Dan and Shell.
Ladbrokes spokesman Warren Lush said: “We have seen a gamble on Jason, particularly in Scotland, but we believe it is too late for the jungle cat. If he did win it would be a disaster for Britain’s bookmakers.
“His supporters have done him proud but Nadia is still the strong favourite.”
Nadia’s odds have been cut from 1/50 to 1/20.
The bookies have got it wrong before – they predicted Jason would be booted out two weeks ago only for viewers to choose Victor.
And they were convinced Shel would go on Wednesday, but Stuart went instead.
Bookmakers have taken more than £5m (€7.5m) on this year’s series, making it the biggest reality TV betting event yet.
Nadia is likely to make more than £1m (€1.5m) if she wins Big Brother.
But she does have something else to fall back on – the Portuguese transsexual has been offered her old job back at Sainsbury’s.
The 27-year-old worked part-time on the cash desk at her local Brookwood branch in Woking, Surrey.
Days before the start of the Channel 4 show she told bosses she was going on holiday.
They were stunned to turn on the TV and see her in the Big Brother house.
But she was so popular at the store during the 18 months she worked there that bosses have kept her job open.
A Sainsbury’s spokeswoman said: “Nadia was a very valued member of staff and she was loved by colleagues and customers alike.
“We had no idea she was going on the programme but we are delighted with how well she has done.
“We are sure Nadia will have lots of job offers when she comes out of the house. But we want her to know her old job is waiting for her and we would love to have her back.”
Nadia, who came to Britain from Madeira to have her sex change operation, worked in the supermarket during the evening and as a bank clerk during the day.