Federal tax withholding - no (but lowered to reflect 9% rate)
SS and Medicare - yes (that is what offsets much of the bite for sales tax, for lower income earners).
So does SS just officially become a welfare program rather than, in theory, being its own separate retirement account?
Also, why does Cain assume if he eliminated the employer paid contribution to Social Security that this money would go to employees in the form of salary/benefits? Some might, over time perhaps most will since it is part of corporate payroll budgets - but there is no guarantee of that at all. Unless pressed to do so, many employers would just treat that as a tax cut and be in no hurry to add that amount to employee salary/benefits.