Bush might have been able to pass a Social Security privatization plan if he had put forth a plan that was a good idea. A big part of Bush's problem is that the plan he is putting forth is only a good idea for investment bankers. This resulted in a plan that even a lot of Republicans don't like and thus will not fight for.
More over, it is obvious from Bush's plan that it will require Social Security be cut down the road to balance the budget. No matter what the White House speakers say, they can't get around the fact that the plan looks like it will always loose money unless Social Security is cut.
How much long term consequences this will have for Bush's term in office, I don't know. Bush has invested enough in this that dropping it now would look like a failure, but the Bush White House has always been very good at ignoring the past and claiming that whatever did happen is exactly what they planned all along.
Jay