But McCain has been supporting the privatization of Social Security for many, many years, not just in this campaign
Bush's 2005 proposal was hardly the first time it's been thought up and put forward - various privatization schemes have been advanced by the Right for decades.
More recently, it was a key point in McCain's 2000 Presidential campaign, for instance.
So Obama's claim is absolutely true, if John McCain and the Republicans had had their way, not just future but current elderly recipients of Social Security could have seen an erosion of their retirement benefits.