Matt Yglesias puts his finger on why you can’t trust political pundits to tell you what’s happening in an election race:
…ordinary people ordinarily just don’t pay attention to politics at all. They don’t think it’s interesting. But … [t]he political press, by contrast, finds electoral contests to be a kind of fascinating game about which it’s amusing to do tons of stories regarding the ins-and-outs of tactical gambits…
The kinds of people who are political reporters are self-selected to enjoy commenting on the race as if it’s a game, simply because talking about politics day in-day out requires them to do just that. To think that they are, in their view of politics, remotely representative of the voting population is ridiculous. In fact, their analysis of political events is highly unlikely to represent the views of the average voter.
It is likely that the pundits are portraying the election contest as far closer than it really is. A landslide is hardly the most interesting thing to comment upon: there will be plenty of time to pick over the bones of the losing campaign when the election’s done. A close contest makes for far more exciting discussion and they probably have an incentive to depict it as such, regardless of the true situation.
I would far rather trust aggregations of information such as you find on prediction markets. However, it may similarly be argued that those who engage in share trading on such markets are not representative; so the aggregate price statistic you see is a biased indicator of the actual probabilities. Which way the distribution of share traders is skewed I don’t know.