Gen. David Petraeus has bought President Bush an additional six months of running room in Iraq, but it will still take a series of miracles to avoid catastrophe there. [IMGCAP(1)]

Petraeus’ military successes on the ground and his promises this week on Capitol Hill of troop reductions and possible lower U.S. casualty levels have kept the political bottom from falling out of Bush’s policy.

Democrats and the anti-war left had hoped that Republicans would be defecting from Bush in droves as the 2008 elections edge closer, but so far it hasn’t happened.

Senate Republican leadership aides expect that if Democrats propose new amendments to cut off war funds or impose deadlines for withdrawal, they will garner no more GOP votes than the four they had in June.

That’s eight short of what’s necessary to break a filibuster and pass a bill and 15 short of overriding a presidential veto.

And, despite a $12 million ad campaign mounted this summer by an anti-war coalition headed by MoveOn.org, only one House Republican, Rep. Jim Walsh (N.Y.), has turned against Bush, while a Democrat, Rep. Brian Baird (Wash.) is now backing perseverance in Iraq.

How long can this go on, especially with Petraeus forecasting — and Bush affirming — that U.S. troop levels will only fall from 160,000 to 130,000 by next summer, just months before the election?

Republicans point to two possibilities that could sustain GOP support: further troop reduction announcements in March or April and a change in the U.S. mission that might reduce U.S. casualties next year.

Petraeus’ superiors at the Pentagon and the U.S. Central Command reportedly are calling for reductions below 100,000 next year. And, as House Minority Whip Roy Blunt (R-Mo.) put it to me, “We’re encouraged by Petraeus’ discussion of a new mission that would get U.S. troops out of combat.”

“We still have troops stationed in Bosnia,” he said. “It’s not a big issue because they are not getting shot at.”

Petraeus told Congress that if Iraqi forces can take the lead role in securing the country, the U.S. mission could “transition” to one of “overwatch.”

Senate Republicans, while sticking with Bush in the face of Democratic deadline and defunding proposals, are likely to push for resolutions calling for a change in the U.S. mission.

So, Bush has succeeded in maintaining control of Iraq policy. But, achieving something that could be called “victory” — and avoiding catastrophic defeat — requires developments in the next year that are hard to foresee.

As one former top U.S. general and diplomat told me, “I think we have another six months to see if the Iraqis can get their act together.

“If they do, and it gives people confidence in sticking with it even longer, then the surge will have been successful.

“If that doesn’t happen,” he said, “it will be like a stool with only one leg. The only underpinning that is going to count with the American people and Congress is whether there is fundamental change among the Iraqis.”

The chief miracle that has to occur for Bush to avoid a debacle in Iraq is national reconciliation and an end to the civil strife that is tearing the country apart.

The U.S. “surge” has suppressed violence in Baghdad somewhat and has bolstered a Sunni rebellion against al-Qaida extremists, but it has not produced the Sunni-Shiite reconciliation necessary for long-term stability.

U.S. Ambassador to Iraq Ryan Crocker told Congress that some “de facto reconciliation” is occurring in the absence of national legislation to distribute power and resources, but terrible ethnic cleansing continues in Baghdad and, in southern Iraq, Shiite militias are battling each other.

Another necessary miracle is a takeover of security responsibilities by Iraqi forces. A commission headed by former NATO commander Gen. James Jones reported that the Iraqi army was increasingly able to fulfill its responsibility, but that the Iraqi National Police was so corrupt and militia-infested that the force needed to be disbanded and rebuilt.

Jones told me in an interview that his biggest surprise in studying Iraq was “how pervasive the threat from Iran is” and that neither U.S. forces nor Iraqis are controlling Iraq’s borders against inflows of weapons and operatives. He said U.S. forces should take that role as part of a “remissioning” that could begin soon.

Ultimately, Bush is caught in this bind. His political support at home depends upon drawing down U.S. forces and reducing their combat role. But Iraqis, expecting a U.S. withdrawal, are preparing for a civil war. Stability in Iraq depends on reconciliation. That is, a miracle.