I agree with most of Ilya’s post below on why political pundits are overconfident that their side will win elections. I would just add an even more cynical point: A lot of political pundits are overconfident simply because they are entertainers who satisfy their audience by pleasing their supporters. Pundits get on TV if people want to watch them. A lot of people will watch if they expect the thrill of hearing a prediction of great news ahead. As a result, a pundit who isn’t always predicting great things for their side is going to have a harder time finding an audience. This doesn’t mean that all pundits are just hacks for their side. But if you want to be a pundit who appears regularly in high-profile venues, it certainly helps.