The reversal of the banning of so many popular Sunni candidates from the looming election is a huge step back from the brink. And it does help support Petraeus' view that the Iraqi leadership is maturing. I've been a deep skeptic about whether this process could stay on track - and, of course, the future is unknowable and the results of the election could provoke another terrifying moment of truth.

But this is clear evidence for cautious optimism. Let's hope it can be sustained.

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