I believe you’re right—the polls are fudged; I’m not sure by how much. But consider this: Intrade represents real money that people are betting. If they relied on polls that can be proven to have been doctored, and they lose, do they have a case of any kind against the pollsters?
Let's think about intrade. They really blew it with Sarah Palin being picked as VP candidate. They are not infallible, in fact they screw up quite frequently.