Even if the tribal elites remain loyal, the alliance poses a larger problem for basic US war aims. The alliance with these tribes serves, necessarily, to strengthen them as political units. Strengthening the tribes invariably weakens the central government. As the tribes are also among the least progressive and least interested in democracy of any Iraqi political constituencies, strengthening them also helps undercut efforts towards democratization. So, to the extent that the US goal remains the creation of a strong, democratic central government, the deal with the Sunni tribal leaders is almost completely at odds with the end that we'd like to see.
So if there is such a thing as success in Anbar, it's qualified at best, and only temporary. As I've explained before in the post I link to above, Iraq is filled to the brim with various groups contending for power. The reason the Sunni are willing to ally with us is because right now, in Anbar province, their biggest problem is al Qaeda. That will change, because the real struggle is not between al Qaeda and Shiite Iraq, but between the Sunnis and the Shiites, and that struggle continues in Baghdad and now in places like Diyalah province. Were the Sunnis in Anbar to suddenly face the threat of violence perpetrated on them by the Iraqi Army or security forces or various Shiite militias, they would immediately shift their efforts to repulsing that threat. In fact that may be the result of any successful effort to contain al Qaeda, as the Sunni leadership in Anbar will realize that they can again focus on their biggest threat. And we, as protectors of the national government, would no longer be their allies.
There was a time when perhaps we could have taken advantage of these ever shifting loyalties to perpetuate some sort of balance among Iraq's various factions. If we ever had the political acuity and willpower to adopt such an approach (something I now seriously doubt we ever possessed) that time is now past. As Hilzoy explains to great length, we have no choice but to let the Iraq civil war burn itself out, because there's nothing we or anyone else can do to stop it. Any remaining strategic options in Iraq must reflect that fact.
UPDATE: Here's an example, via Glenn Greenwald, of the sort of triumphalism echoed around the pro-war blogosphere over the Anbar "success":
What I really learned today is the lengths many will go to deny the facts on the ground--when they have no knowledge of those facts--and the fear they have of success in Iraq.
To them the Anbar Awakening cannot be true, because if it is, the surge will be extended, the Petraeus plan will be implemented fully accross the country and the enterprise could prove successful.
And if the enterprise is successful, they were wrong. Their identities being so wrapped up in their opinions and belief that Iraq is and will be a failure, that their egos will not allow them to be wrong. Admission that they were wrong is tantamount to self-identity suicide.
Therefore, the Awakening does not exist, what I saw in late May and previously in April does not exist. It is not happening. Everyone is being duped and lied to. Those Iraqi tribesmen? Actors. It is all astroturfed. After all Glenn Greenwald wrote a best selling book and I'm only a guy who spent two months in Al Anbar this Spring.
Now I admire anybody who's actually willing to go to Iraq and get a look at conditions on the ground so they can make up for their own minds what's really happening over there. Unfortunately, those who do-at least on the right-do not appear to understand the limitations of this approach, nor do they seem to understand some basic facts about Iraq. For one, note the hastily arrived at conclusion that "if the [Anbar Awakening] is true, the surge will be extended, the Petraeus plan will be implemented fully accross the country and the enterprise could prove successful." No facts are cited that would support such a conclusion. This is because there are no facts to support such a conclusion. Instead, it appears as if this will all happen by magic. Peace in Anbar will somehow spread on its own throughout all of Iraq, despite the fact any "peace" in Anbar is the direct result of conditions local to Anbar that don't have as much relevance in Baghdad, or Diyala, or Kurdistan, or Najaf, or Nasiriyah, and nothing at all to do with the surge strategy currently being implemented in Baghdad and now Diyalah that post-dates the stability in Anbar. This "peace by magic" argument is pretty much the only one being put forth by those who cite to the Anbar success. It's not enough to change any reasonable person's mind, let alone the actual conditions in Iraq, but it is enough to keep the pro-war right warm at night.
Of course, that's because this sort of "reporting" is merely the dissemination of propaganda. Note that the success in Anbar is referred to as the "Anbar Awakening" (capitalized), a slogan handy for commentators and bloggers on the right. Note the reverse psychology, wherein JD Johannes accuses those on the left of pretty much what those on the right are guilty of: "...if the enterprise is successful, they were wrong. Their identities being so wrapped up in their opinions and belief that Iraq is and will be a failure, that their egos will not allow them to be wrong. Admission that they were wrong is tantamount to self-identity suicide." Change two words-"if the enterprise fails"-and that paragraph would be an exact summation of why those on the pro-war right so badly need the surge to succeed, and are willing to make magical arguments to "prove" its success.
Johannes is not there to "report" on progress in Iraq. Here's there to prove it. To him, Sunni gunmen fighting al Qaeda is proof enough that our entire mission in Iraq, as typified in the surge strategy, is succeeding. There's no differentiation between Anbar and other Iraqi provinces, no exploration of how the surge is unrelated to and post-dates the relative peace in Anbar, and no exploration of how Anbar relates to our overall strategy, or even what our overall strategy is. Thus, such reporting is not only not informative, but it's actually harmful to our understanding of the situation in Iraq. Fortunately, the majority of the American public no longer seems to be swayed by arguments like these, a fact that those on the right seem completely incapable of understanding.