On the fifth anniversary of the start of the Iraq war, Americans should be holding the administration responsible for its record in Iraq.

I use the word "should" advisedly. Many people will argue that it is useless to rehash the past. We are where we are. Let's focus in presidential elections on who best can handle Iraq's future.

But Iraq's future cannot be divorced from U.S. policies that led to the devastation of that country. Tens of thousands (or more) of Iraqi civilians and thousands of American soldiers did not die because of mistakes made by Martians. They died because of gross White House errors in planning the Iraq war and stunning incompetence after Baghdad fell.

The Iraq options of the next president will be thoroughly circumscribed by the administration's actions. That's true whether the president is Hillary Clinton, Barack Obama or John McCain.

Future Iraq policy will have to deal with the following legacy: The Bush team dismantled Iraq's social fabric and institutions (already degraded by Saddam Hussein), but had no plan for rebuilding. It failed to provide postwar security, which enabled criminality to flourish and al-Qaida to set up cells that had not been there before.

The Bush team pressed Iraqis to adopt a constitution and an election system that exacerbated sectarian divisions and created a weak, dysfunctional central government. This system ensured the domination of religious parties in a country that was once secular.

And Bush policies guaranteed that Iran would become the most powerful player in Iraq. Two weeks ago, Iraqi leaders rolled out the red carpet for Iran's President Mahmoud Ahmadinejad, who gloated that he could travel freely around Baghdad while the American president can only make stealth visits.

These policies will haunt the next president.

Yes, some progress has been made over the past year in Iraq. But the "surge" has not fostered the political reconciliation that would enable substantial numbers of U.S. troops to leave.

In December I saw tentative efforts to form new political alliances across sectarian lines, bringing some Sunni and Shiite groups together — a politics based on shared interests rather than sect. These prospects are still alive, and they are Iraq's (and our) best hope, but they are already fraying.

Sunni militias that once fought us but are now on the U.S. payroll see little sign that the Shiite-led government will absorb them into government security forces or give them jobs, as the Americans had promised. So the Sunni militias are biding their time until we start leaving. Shiite militias are also holding their fire until U.S. troops draw down.

The argument that an exit timeline will force the Iraqis to reconcile is mistaken. A timeline would only set the stage for renewed sectarian fighting. It would destroy what remaining leverage America has with Iraqi factions and Iraq's neighbors. We would leave behind a bleeding, failed state.

Yet the McCain thesis — stay on for decades — won't wash either. We cannot keep more than 100,000 troops in Iraq for much longer.

This reality was underscored by the stunning resignation last week of Adm. William Fallon, head of the military's Central Command, which oversees the Middle East and South Asia. Like many U.S. commanders, Fallon worried that Iraq was distracting America from the bigger security picture, such as problems in Pakistan, Afghanistan and Iran. He also felt that repeated Iraq tours were degrading the quality and morale of the forces.

Fallon quit because his position put him at untenable odds with the White House — and with Gen. David Petraeus. But Petraeus, sitting in Baghdad, has the Sisyphean task of trying to undo the mess made by the administration. He recognizes that the current gains are likely to be reversed if a sharper drawdown is attempted in the next year. Both men have valid positions, but both are trapped by the policies of the past five years.

The next president will be similarly entangled.

The only hope for a decent Iraq exit may lie with a new U.S. approach to the region, emphasizing tough diplomacy that draws Iraq's neighbors into a new regional security arrangement. An exit timeline would become part of those negotiations. But such talks would require America to broaden its dealings with Iran, which can now drive a much harder bargain than five years ago.

The Bush legacy has left the Iraq situation so messy that none can be certain where things will stand in a year's time or the path the next president would follow — whether that president is Obama or Clinton or McCain.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer. Reach her at trubin@phillynews.com.