I don't think Jeopardy would fix the show. I suppose it would be easy; just get one really smart contestant who is fast on the button, and have lower quality contestants as his challengers.
There was a big US game show fixing scandal in the 1950s, where some contestants were supplied the answers in advance and told how to react (such as wringing hands or wiping a sweaty brow). There were congressional hearings, and the public was angry.
"The popularity of quiz games was staggering. In August of 1955 approximately 32 million television sets and 47,560,000 viewers, almost one third of the nation, tuned in to see The $64,000 Question. (Anderson, 8).
By 1958, no one was laughing anymore. Grabbing the attention of the public even more than the shows themselves were the scandals which emerged around them. The public's naive trust had evolved into suspicious cynicism because it had learned that many of the shows were rigged. As can be imagined, this caused great disgust among viewers. The supposed winners, for whom Americans had rooted and had become dedicated weekly fans, had in fact been supplied with answers in advance. These scandals prompted Congressional hearings and investigations which further shocked the public. Even though there were no laws prohibiting the fixing of game shows, both the networks and their sponsors acknowledged the public's scorn and kept the shows off of the air to allow these turbulent waters to settle."...
http://www.plosin.com/beatbegins/projects/venanzi.html
"...