Everybody agrees that political journalists and pundits were big losers in the general election. As Jon Stone points out, many of their cherished presuppositions turned out to be wrong.

Here's a theory as to why. It's because of deformation professionelle. Every occupation has a way of approaching issues which, whilst useful in many ways, also tends to distort their perspective. For example, engineers over-rate the extent to which everything is an engineering problem; lawyers put too much faith in the power of the law; and economists have traditionally over-emphasized extrinsic incentives.

Political commentators are no different. Their perspective too is distorted - a distortion is magnified by the sort of groupthink described by George Monbiot.

One such distortion is that they pay too much attention to Westminster and too little to the ground truth of grassroots politics. For example, in his admirable review of his errors* John Rentoul says he under-estimated voters' hostility to capitalism and desire for optimism and compassion in a leader. This might be because his antennae were too attuned to Westminster and insufficiently to the country.

This was an especially grave mistake because Corbynism is a different type of politics. It pays less heed to the Blairite virtues of day-to-day news management and more to building party membership, mobilizing what Phil calls the networked worker and getting out the youth vote (where "youth is anyone under 47).

John wasn't alone in this of course. Jonathan Dean says of political scientists:

had we moved our gaze beyond Westminster-centred electoral politics to encompass, for instance, work by cultural studies scholars on the connections between youth culture and ideology, black feminists on race, gender and political solidarity, or literature on social movements and activism, we might have been better able to properly make sense of Corbynism.

Relatedly, pundits pay too much attention to personalities and too little to policy. They commit the error of which Richard Sennett complained 40 years ago:

A political leader running for office is spoken of as "credible" or "legitimate" in terms of what kind of man he is, rather than in terms of the actions or programmes he espouses. The obsession with persons at the expense of more impersonal social relations is like a filter which discolours our rational understanding of society. (The Fall of Public Man, p4)

Tom Mills points to a good example of this. The leaking of Labour's manifesto was reported as a failure of Corbyn's party management when it could instead have been seen as a set of popular policies.

Such a focus upon political leaders would not be so bad if it were clear-eyed. But it's not. "Strong" leadership is seen too much in terms of party unity, and too little in terms of good, inclusive decision-making. We know now that May was gravely weakened by her excessive reliance on too narrow a group of advisors - but Westminster journalists were perhaps better at pointing this out in hindsight than they were weeks ago.

Finally (for now!), there's been a tendency to regard politics as an exercise in marketing. Far too often, Corbyn and his policies were dismissed as simply "unelectable". One happy effect of this election should be that Corbyn's critics will speak less of electability and instead debate policies on their (de)merits.

My point here is not that political correspondents are uniquely biased: all professionals are. What I am doing, though, is raising questions about the BBC. How can we reconcile the organization's supposed commitment to impartiality with the fact that its Westminster correspondents have particular biases?

* I don't like the words "error" and "mistake". They have connotations of deviation from a normal condition of being right when in fact in emergent systems such as politics, economics (and financial markets) mistakes are so common as to be routine. We should stigmatize mistakes less, but put more stigma onto the failure to learn from them.