Two words: sex scandal. I'll come back to that but first, while his departure may not be necessary to save Obama, Geithner is beginning to look like a guy with an overloaded cart at the baggage claim area, scampering alongside of it as the bags on top of the pile begin to slide off. It's hard to push the cart when you're doing that. And if somebody comes after him yelling, "Hey buddy, you forgot this one!" and throws another on the pile...
That's when the A team starts to look for the graceful exit, usually centering around the idea that while the official has done nothing wrong, he doesn't want to become a distraction.
Unfortunately, in this case it will be seen as an admission of failure, that this was the wrong guy for the job, his appointment was a huge mistake, the presidency will be seen as in disarray, and there will generally be hell to pay.
Which brings us back to sex. This is the one piece of baggage which Geithner may not have on the carousel. But finding a ring of high class hookers in Washington is like going outside and throwing a rock, in pretty much any direction. One appointment with a professional, any time of the day or night. Then, a generous tip if she will agree to blow the whistle on him, a couple of days of denial, then the public apology, the supportive family, the resignation, and the fact that none of this will reflect poorly on the President! He will be deeply saddened, and accept the resignation immediately.
The press will be in their familiar tizzy, so much so that the whole subject of the bailout, the economy, the bonuses, the banks (what banks?) will be off the radar screen entirely. Instead, there will be pictures, lots of pictures, breathless profiles of the professional woman, and plenty of commentary on all aspects of the scandal. And we can find a new Secretary of the Treasury, not a member of the banking elite, (may I suggest Robert Reich?) and move on!