Why, then, are we obsessing over Social Security, which is not really that big a deal, and ignoring Medicare, which has serious problems in both the short term and the long term?
As near as I can tell, the answer is twofold. First, Social Security provides Republicans with a chance to introduce a conservative nostrum that they've long pined for: private accounts. We don't need them, and they won't actually do anything to solve whatever problems Social Security might have, but an invented crisis is a good excuse to introduce them anyway. Conversely, there's no way to plausibly pretend that private accounts will save Medicare, so why bother?
Second, Social Security is relatively easy to deal with since it's just a pure funding issue: you can raise taxes, cut benefits, or borrow more. It's pretty simple to grasp.
Conversely, Medicare reform is really, really hard. You've got the same funding issues as Social Security, except much bigger and much closer; and in addition you also have to face up to spiralling healthcare costs. And figuring out a way to contain healthcare costs is a subject that nobody wants to tackle. Not Democrats and definitely not Republicans.
It's easy to agree with this analysis, especially considering that much of the increase in Medicare costs are related to administrative costs. I mean, here we are, the last industrialized country NOT to have health care for all its citizens, and we're being scared away by politicians blabbering about "the perils of socialised medicine"? Gimme a break! If I'm feeling ambitious this afternoon, maybe I'll look for more data on what our health care system really costs us.