Greenspan: Country can't afford McCain tax cuts

From the AP.

The linked story indicates that McCain has pledged to end pork-barrel spending, “unnecessary” government programs, and overhauling Social Security and Medicare.

Isn’t this extremely wishful thinking, though? How is a president, regardless of party, going to completely control what bills Congress passes - especially if they have the 2/3 majority needed to override a veto? What exactly is an “unnecessary” government program and how is he going to eliminate enough programs to make a substantive difference (i.e. at least a few hundred million dollars if not billions)? How is he going to overhaul Social Security and Medicare enough so that he simultaneously saves the government billions while also not curtailing these programs so that they aren’t reduced to uselessness or millions aren’t booted out?