In a new column for Bloomberg View I blame the failure of the deficit supercommittee on polarization--who doesn't?--but then try to answer the harder question: what is driving polarization?

One school of thought says that voters [much as they claim to dislike polarization] only think they want compromise. If they saw it, they wouldn't like it -- and they don't care about budget deficits as much as they say. The Simpson-Bowles mixture of tax increases and entitlement cuts would be intensely unpopular, on this view. Electorally, it makes better sense for Democrats to defend entitlements above all and for Republicans to oppose tax increases above all, and for both sides merely to pretend (like voters) to care about the deficit.

I don't believe it. I have a higher opinion of voters. Most of them, I think, would support the Simpson-Bowles approach if it were offered to them and properly explained. Somebody ought to try it, at least.

My own theory of U.S. political paralysis is not that a deeply divided electorate is getting what it asks for, but that the balance of power between party leaders and party activists has moved too far in favor of activists. This leaves the center disenfranchised.

If so, why are activists getting the upper hand? Partly, I would guess, because technology is making it easier for them to gather with other activists. This encourages views to harden (the echo-chamber effect) and makes it easier to organize and apply pressure. One thing that troubles me about this guess, however, is that technology affords those opportunities everywhere, and you do not see increasing political polarization everywhere.

A similar problem also arises, by the way, for Peter Orszag's view, that polarization is driven by rising income inequality. (Income inequality drives residential segregation by income, which drives residential segregation by political party, which increases polarization.) Many countries have seen rising income inequality in recent years; few have seen so marked a rise in political polarization.

You might reply, what matters is the level of inequality not the rate of change. In that case, why was American politics so consensual (by international standards) a generation ago? The level of US inequality was high (by international standards) then too. 

Taking one step back, Orzsag believes that American politics has become more polarized because American voters have become more polarized. To some extent, maybe. But the electorate still has a wide (and electorally decisive) middle and Congress no longer does. That, surely, is the puzzle.