Good God Girty! There is no "surplus" in the "trust fund." There is money remaining, but it is quickly being depleted by us Boomers who are drawing it down. If and when it runs down to zero (it won't), SS benefits CANNOT BE PAID OUT OF GENERAL FUNDS. This is part of the legal fiction that makes SS arguably Constitutional: It doesn't and can't use general fund dollars!*
If the fund were to run dry, SS would move to a pay-go arrangement, and benefits would be cut, across the board, by about 20%. But Congress will never let this happen. They would all be voted out immediately. They will come up with a solution, the main part of which will be the elimination of the cap on wages subject to the FICA tax.
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* Socialized medicine, or whatever it ends up being called, will require ANOTHER "payroll tax" which wage-earners will have to pay in addition to the SS and Medicare payroll taxes. OR the Medicare tax will be dramatically increased to cover the additional cost. The hope would be that the health insurance premiums we (or our employers) pay would be removed, and the net cost to the taxpayers would be zero.