[H]ere is what I would suggest as a responsible stance toward Iraq. Others, including Iraqi politicians, have already suggested most of these things...
1) US ground troops should be withdrawn ASAP from urban areas as a first step. Iraqi police will just have to do the policing. We are no good at it. If local militias take over, that is the Iraqi government's problem. The prime minister will have to either compromise with the militia leaders or send in other Iraqi militias to take them on. Who runs Iraqi cities can no longer be a primary concern of the US military. Our troops are warriors, not traffic cops.
2) In the second phase of withdrawal, most US ground troops would steadily be brought out of Iraq.
3) For as long as the elected Iraqi government wanted it, the US would offer the new Iraqi military and security forces close air support in any firefight they have with guerrilla or other rebellious forces. (I.e. we would replicate our tactics in Afghanistan of providing the air force for the Northern Alliance infantry and cavalry.) I concede that this tactic will get some US Blackhawks shot down from time to time, and won't be painless. But it could prevent the outbreak of fullscale war. This way of proceeding, which was opened up by the Afghanistan War of 2001-2002, and which depends on smart weapons and having allies on the ground, is the major difference between today and the Vietnam era, when dumb bombs (and even carpet bombing) couldn't have been deployed effectively to ensure the enemy did not take or hold substantial territory. [I am not advocating bombing civilian neighborhoods of cities; I am talking about intervening in set-piece battles of the sort that will become possible in the absence of US ground troops.]
4) With the agreement of the elected Iraqi government, the US would prevent any guerrilla force from fielding any large number of fighters for set piece battles. Such large units of militiamen attempting to march from Anbar on Baghdad, e.g., would be destroyed by AC-130s and other US air weaponry suitable to this purpose. This tactic cannot prevent the current campaign of car bombings, but it can stop a full-scale Lebanon or Afghanistan-style civil war from erupting.
5) In addition to the service of its air forces, the US would offer targeted military aid to ensure the stability of the Iraqi government. It would help protect key political figures from assassination, and it would give the Iraqi government help in preventing pipeline sabotage so as to increase Iraqi petroleum revenues and strengthen the new government.
6) The US would help rapidly build an Iraqi armor corps. The new Iraqi military's lack of tanks is almost certainly because the US is afraid they might be turned on US troops in a crisis. Once US ground troops are out, there is no reason not to let the Iraqi military just import a lot of tanks and train the new Iraqi army in using them.
7) The US should demand as a quid pro quo for further help that elections in Iraq henceforward be held on a district basis so as to ensure proper representation in parliament for the Sunni Arab provinces. This step is necessary if there is to be any hope of drawing the Sunni Arab political elites into the new government.
8) The US should demand as a quid pro quo for further help that the Iraqi government announce an amnesty for all former Baath Party members who cannot be proven to have committed serious crimes, including crimes against humanity. Former Baathists who have been fired from the schools and civil bureaucracy must be reinstated, and no further firings are to take place. (This step is key in convincing the old Sunni Arab elites that they won't be screwed over in the new Iraq.)
9) Congress must rewrite the laws governing US reconstruction aid to Iraq so as to take out provisions that Iraqis must where possible use US companies or materiel. All of the reconstruction money should go directly to Iraqi firms, so as to help jump-start the economy.
10) The US should join the regular meetings of the foreign ministers of Iraq's neighbors, with Condi Rice in attendance, along with Russian Foreign Minister Sergey Lavrov, employing a 6 + 2 diplomatic track to help put Iraq back on its feet through diplomacy and multilateral aid. This step will require that the Bush administration cease threatening regularly to bomb Tehran or to overthrow the governments of Syria and Iran. For the sake of getting out of Iraq without a world-class economic disaster, the US will just have to deal with the real world, which contains Iran and Syria. The US is now a Middle Eastern Power, not just a New World one, and as such it needs to use Iraq's neighbors to calm their clients within Iraq. This goal cannot be achieved through simple intimidation, more especially since, with half of all fighting units bogged down in Iraq, the US is in no position to follow through on its threats and everyone knows it.
I can't guarantee that these steps will resolve the crisis in the short or even medium term. But I do think that, if taken together, they would allow us to get the ground troops out without risking a big civil war or a destabilization of the Middle East. Once Iraq can stand on its own feet, I am quite sure that the Grand Ayatollah in Najaf will just give a fatwa for complete US withdrawal, and the US will have to acquiesce, as it did in similar circumstances in the Philippines.