The British public is convinced David Blaine cannot survive in his perspex box for 44 days, bookmakers have said.
Blaine faces further torment from the public during his 44-day stunt
"Almost all" of the bets placed on his endurance stunt are for him to fail, a spokesman for William Hill said.
"His chances are getting slimmer, like him," the spokesman added - but the bookmaker still expects him to do it.
Blaine, who is surviving on just water, is receiving as much abuse as support and on Wednesday a man was injured after trying to throw lemons at him.
The William Hill spokesman said: "Despite the fact that he has achieved every other target he has set himself, people seem to think that this may just be one stunt too far."
After 12 days of being suspended 30 feet (nine metres) above the ground next to London's Tower Bridge, Blaine's odds of succeeding have been lengthened from 2/9 to 4/9.
He has been taunted by members of the public and several tabloids, who have played tricks ranging from stripping off to grilling food below him.
Security has been stepped up around Blaine's box
And, according to the press, his persecution is set to continue.
The Sun newspaper reported that a website for gay men has asked its users to throw sausages at his box, while the Daily Express said a man would sit in another perspex box below him, allowed to drink anything he likes - except water.
On Tuesday, a man was charged with criminal damage and threatening behaviour after allegedly trying to cut the water line going into the illusionist's box.
And on Wednesday, press photographs showed a man bleeding from the face after a confrontation with a security guard.
A spokesman for Blaine, 30, said two people were "throwing missiles" from shopping bags when a security guard tried to remove the bags.
"When the security guard went over to check the bag himself, the individual threw a punch," he said.
"The security guard then reacted with one single defensive blow."
The magician has also been taunted by people hitting golf balls at his box, been woken by drumming and a burger has been flown up on a remote-controlled helicopter.
Blaine-baiters have been discussing tactics on a website devoted to harrassing the showman, Wake David.
Stunts suggested include setting up hundreds of alarm clocks to keep him awake, or having a "real magician" perform nearby to "punch a hole in his ego".
One of the people behind Wake David, web designer Jason Robinson, 33, from north London, told BBC News Online: "We think the stunt's really poor - it's just rubbish. 44 days of this is just boring.
"He's got a God complex and it's embarrassing to other magicians."
Mr Robinson echoed comments by London mayor Ken Livingstone - whose City Hall base is next to Blaine's box - who said the stunt was insulting to the families of people who had starved themselves for political reasons, such as IRA prisoners in the 1980s.
"At least in Northern Ireland people starved themselves for a cause," Mr Robinson said.
Blaine's exploits are also being filmed for TV shows on Channel 4 and Sky One.