With his new Iraq policy, President Bush essentially has written off any prospect of regaining broad support at home for his course of action, in the slender hope of finding the key to military success and political agreements in Baghdad.
It is a huge personal gamble, one that has triggered a debate which may well dominate the final two years of Bush's tenure.
Interestingly, Bush and his critics start from the same premise: The ultimate solution in Iraq is political, not military. In his televised speech Wednesday night, Bush said, "Only Iraqis can end the sectarian violence and secure their people."
That will require concrete steps toward national unification with the Sunni minority and the Kurds which the Shiite-dominated government of Prime Minister Nouri al-Maliki has balked at taking for the past year.
And Bush and his critics share a second premise: That government must be nudged into action - or Iraq is lost.
The Iraq Study Group, the bipartisan panel headed by James A. Baker III and Lee Hamilton, argued that the most effective signal to Maliki and his associates would be to announce plans for a phased withdrawal of American troops in the first quarter of next year. That policy would have commanded strong support in the Congress elected last November and, if polls are correct, among the American people.
Bush chose another course, arguing that any early pullout or loss of American assistance would lead to "a collapse of the Iraqi government, tear the country apart and result in mass killings on an unimaginable scale."
That does not say much about the viability of that government, but there is certainly a measurable risk that Bush may be right about the consequences.
In any case, he has chosen to send Maliki a very different signal - more troops under looser terms of engagement, ready to support Iraqi forces in an effort to purge Baghdad of rival Sunni and Shiite militias.
In doing this, Bush has adopted the view of John McCain, Joe Lieberman and the neo-cons, namely, "The most urgent priority for success in Iraq is security, especially in Baghdad."
But he has claimed to be dealing with the political problem at the same time - by informing Maliki that "America's commitment is not open-ended," and by reiterating the now-familiar set of steps needed for political progress - division of oil revenues, constitutional reform, provincial elections, de-Baathification - that the Maliki government has long resisted.
Bush said he has Maliki's word that all this will happen - and that there will be an end to the unspoken policy of targeting Sunnis while protecting Shiite militias.
When I asked a National Security Council official why the promise should be taken seriously, after so many disappointments in the past year, he said the prime minister now faces not just external pressure from the United States, but also the urgings of "other moderate elements" in his own coalition who are weary of the fighting.
A skeptic would say that Bush has sacrificed the support of moderates at home - the Republican as well as Democratic lawmakers voicing skepticism about his plan - for some supposed "moderates" in Baghdad.
For this gamble to work, a lot of implausible things have to happen. Maliki's governing coalition, which includes the party of Moqtada al-Sadr, will have to steel itself to send troops into the neighborhoods controlled by Sadr's own Mahdi Army. Defense Secretary Robert Gates says this will happen, but the promise remains to be tested.
Also unproved is the capacity of the Iraqi army and police force, which are supposed to be "in the lead," with American troops in support, in clearing out Baghdad. The army was disbanded in a reckless decision soon after the fall of Saddam Hussein, and is only now being slowly rebuilt. The police force is notoriously overrun with sectarian militias.
When Bush draws a picture of Iraqi army and police brigades going "door-to-door to gain the trust of Baghdad residents," he has to hope those cops aren't regarded as assassins disguised in uniform when they go into Sunni neighborhoods.
And then there are those politicians in Baghdad - the ones Bush is gambling can find consensus in a country that has known national unity only under a dictator.
Everyone acknowledges there is no risk-free way of solving the mess in Iraq. Bush has chosen a way that guarantees what was forecast here just a month ago: "a foreign policy and national security debate as consequential as any this nation and its allies have faced since the start of World War II."
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