Gen. Petraeus and his brain trust have devised the best possible Plan F, given the resources available to the Pentagon and declining patience for the war at home. But the Achilles heel of this latest effort is the Maliki government. It is becoming increasingly clear to all in Baghdad that its interests—seeking power and treasure for its Shiite backers—diverge sharply from those of the U.S.-led coalition. Even if Gen. Petraeus' plan succeeds on the streets of the city, it will fail in the gilded palaces of the Green Zone. Maliki and his supporters desire no rapprochement with the Sunnis and no meaningful power-sharing arrangement with the Sunnis and the Kurds. Indeed, Maliki can barely hold his own governing coalition together, as evidenced by the Sadr bloc's resignation from the government this week and the fighting in Basra over oil and power.
Plan F will fail if (or when) the Maliki government fails, even if it improves security. At that point, we will have run out of options, having tried every conceivable strategy for Iraq. It will then be time for Plan G: Get out.
That's assuming the plan works. Which as evidenced by the bombings yesterday, is no decent assumption at all.