How can Intrade be more accurate than polls when it is completely based on polls? Maybe someone believes the longshot will win because he and his relatives will vote that way, but most people are trying to predict the winner (unless you also get $$ for place and show like in horseracing). The most accurate way to predict the winner is to follow the polls, or conduct your own, which is really impractical. So forgive my ignorance again, but how does Intrade predict better than a poll?
Read the efficacy article, it answers your question.