Victor Davis Hanson gives those who argue that we should set a date for Iraq to get its act together and that if they don't meet it we should begin withdrawing immediately something to think about:
As for the Iranian crisis, the only peaceful solution, given Russian meddling and Western fear over oil prices, may be through the emergence of democracy in Iraq, which would then galvanize dissidents in Iran. Anyone who rules out force in dealing with Iran's nuclear ambitions should support unequivocally the democratic experiment in Iraq.
An Iraqi democracy may well serve as a model for Iranians tired of the oppression of the imamocracy they've endured for thirty years. If Iraq is allowed to fail, however, then it will exert no positive pressure on Iran to change, and the current leadership in Tehran will continue its mad pursuit of nuclear weapons.
In other words, one consequence of failure to "stay the course" in Iraq is that it will become more likely that it will be necessary to go to war with Iran. No one who shudders at that prospect should be urging us to get out of Iraq even one day before that country is stable and able to go it alone against its enemies.