The next US president will inherit 140,000 troops in Iraq and no clear plan of what to do with them. That is the bottom line of the report that General David Petraeus is likely to present to Congress today.

He is expected to recommend a drawdown of about 20,000 troops to the level before the “surge”, and then a pause. But then what? He and Ambassador Ryan Crocker will have the same tale to tell: a year of some military success, undermined by paralysis in the Iraqi Government, which has brought Iraq no closer to a political settlement. None of the factors that has calmed the violence, such as the support of Sunni tribes or the “ceasefire” of Shia militias, can be assumed to be permanent.

And none of the “battleplans” of the three candidates gets to grips with this portrait, although John McCain’s, in its promise of unlimited military bounty, could most easily cope with it. Their latest plans are fixated on the number of US troops they say they are prepared to keep there, not the problem they will have to solve.

McCain’s is simplest (and most memorable, given his vow to stay “for a hundred years” if necessary). He argues that “a greater military commitment now is necessary if we are to achieve long-term success in Iraq”. Petraeus and Crocker would probably not quibble with the commitment – but it will be a surprise if they talk, as McCain still does, of “success” resembling the original US aims of installing a representative democracy. There is little discussion of the sectarian rifts within Iraq, and of what the US might best do to bridge them.

Barack Obama acknowledges that problem but argues that “the best way to press Iraq’s leaders to take responsibility for their future is to make it clear that we are leaving”. Perhaps, but if it doesn’t work what then? He also offers “the most aggressive diplomatic effort in recent American history to reach a new compact on the stability of Iraq and the Middle East”. The pledge for engagement is surely on the right lines, although few in the region will appreciate the prospect of an “aggressive effort” heading their way. This is written for the audience at home, with no thought for its resonance in the region.

Hillary Clinton’s position has become similar to Obama’s. She said [on March 17] that her first step would be “to bring our troops home and send the strongest possible message to the Iraqis that they must take responsibility for their own future”. And supposing that they don’t? Her commitment to start bringing home troops at the rate of “one to two brigades a month” within the first 60 days of becoming president does not take account of the danger to US interests from withdrawing. Her swipe at private security contractors, saying that she would ultimately ban them, is myopic.

The candidates are right that they do not need to take responsibility for the US’s predicament in Iraq. But they will for the consequences of its future action. None of them, in competing to offer voters an account of precisely how many US troops will remain, has allowed for the complexity of the picture that Petraeus will lay out today.

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