In one of the biggest turnarounds in the show's history, Gina has gone from being the most unpopular housemate ever to the 11/4 favourite.
Gina began this year's series as a 100/1 rank outsider and her odds have tumbled on a daily basis as she causes mayhem in the house.
Jack and Joe find themselves as the second favourites at 4/1 with Sam next in line at 9/2.
On the other hand, previous favourite Wolfy is now the 50/1 outsider.
Jessica Bridge of Ladbrokes said: "We've never seen odds crash like this in Big Brother history. Punters are refusing to back any other housemates for glory this summer."
As we enter week four (already!) of the series, who are you currently backing to win? Vote in our latest popularity poll of the series below...
Big Brother 2013 continues to air on Channel 5 every night.
Ladbrokes latest betting
Winner of BB
Jack and Joe 4/1