George W. Bush's presidency obviously has not been a smooth ride. The Democrats clearly were never all that taken with him in the first place. The country's independents also have not supported the president for some time. For this group, Bush's perceived unawareness of the severity of the Hurricane Katrina aftermath was the killing blow from which their confidence in the White House has never recovered. But while a president prefers to rule with the support of the country's independents, it is not a requirement. So long as his own party holds, even an unpopular president can do many things.

Bush's problem is that Republican loyalty now appears broken as well. The party comprises three factions: business interests, social conservatives and national security conservatives. Keeping business interests happy is normally simple for a Republican leader, but on Bush's watch, the presidential veto has not yet been used to limit spending. Consequently, the budget deficit has ballooned, and business Republicans' loyalty is no longer a given. Social conservatives feel equally betrayed.

Even this is manageable. On most policies -- especially foreign policy issues such as Iraq -- the only thing a president needs is to make sure his opponents cannot override his vetoes. The U.S. Constitution is extraordinarily clear that the executive branch executes state policy. So long as Congress cannot impose policy prescriptions over the presidential veto, the president remains firmly in control.

This is why this week's events are so critical. The seemingly never-ending nature of the war and the White House's my-way-or-the-highway policies appear to have broken the normally unbreakable portion of the Republican coalition -- national security conservatives. Of the 49 Republican senators, by Stratfor's count, five long ago left the president's camp on the issue of Iraq, and nine more have left within the past month -- seven of them this week alone. These are not dilettantes. Sens. Snowe, Hagel, John Sununu and Richard Lugar are part and parcel of the current generation's core U.S. defense thinkers. No president can simply ignore it when people like these run up the red flag.

While there obviously is a difference between disenchantment with Iraq policy and an all-out rebellion against presidential authority, Democrats and disaffected Republicans now hold 64 votes in the Senate -- tantalizingly close to the 67-seat, veto-proof, across-the-aisle coalition needed to bypass the president. (This 64-seat majority does not include erstwhile Democrat Sen. Joseph Lieberman.)

The momentum is certainly against Bush, and -- barring a very impressive rabbit-from-the-hat trick -- domestic opinion about Iraq will be impossible to turn around. In the meantime, the Iraqi government is clearly not on the verge of acting like a functional ruling body. And those opposed to a U.S.-Iranian deal -- especially foreign jihadists and other groups inside Iraq -- are sparing no effort to turn the region into a bloodbath.

The bitter irony, as far as Bush is concerned, is that the ultimate rabbit -- a comprehensive deal with Iran over the future of Iraq that ends the war in as conclusive a manner as possible -- could actually end the Bush presidency as well and push that 64 up to 67. Any initial U.S.-Iranian deal will require reining in rogue elements. Hence, even if things from this point on go swimmingly, the violence is certain to get worse before it gets better.

Iran and the United States have been going back and forth for years over a potential Iraq settlement. At every turn, each has tested the other's nerve and attempted to appear tougher than it actually is. The Iranians know that if they do not seal a deal soon, they might have to start from scratch, not only with a new U.S. administration but also with an administration intent on using national security issues to prove itself worthy of the public's trust. If Iran cannot get a deal soon, it might not get one at all -- and that sets the stage for possible Iranian concessions due to American weaknesses.