Tyler Cowen is my favorite conservative. Sometimes I actually agree with -- not very much, but sometimes I do. Today in his New York Times article he advocates means testing for Medicare. He acknowledges the possibility that means testing will make Medicare a welfare program, causing it to lose support -- but he suggests that things are so dire we do not have another choice he does not seem to take seriously Mark Thoma's suggestion that single-payer could create substantial cost savings.
I am not sure how big a threat Medicare really is. Any sane political system would find massive savings in the defense budget, but sanity is a scarce commodity. Taxes on the very rich and taxes on purely speculative activities could go a long way to supplement Medicare. Unfortunately, such policies will not be discussed outside of third-party politics.