As Blake affirms, this has a lot to do with Ryan's constant promise that the Romney-Ryan regime will not touch the Medicare plans of people currently over 55. Not only that, Ryan/Romney will restore funding to Medicare. Obama is "changing the program forever." Ryan will "protect and strengthen" it. Look, a TV ad!
The reason Ryan gets away with this is the reason that Republicans won the Medicare issue in 2010, taking seniors from a 50-50 vote to a 60-40 pro-GOP vote. He puts Medicare, theoretically, in a sort of lock-box. He promises to treat it separately from every other government program, and promises seniors of a certain age that they won't have to sacrifice.
The upshot of all this, of course, is that Medicare can never be reformed. Both parties can talk about reform all they want, but when the campaign rubber hits the electoral road they know that attacking cuts to Medicare is the way to win votes. And if both Democrats and Republicans take turns bashing anyone who has the gall to cut back Medicare spending, then Medicare spending will never get cut back.
On a wonky note, it's worth pointing out just how outrageous this whole "no one over 55" approach is. If you don't want to rein in Medicare growth in the first place, that's fine. But if you do want to rein in Medicare growth, current and near seniors are the #1 group that should be required to share in the pain. Seniors all like to think that they're just getting their due from a system they paid into all their lives, but it ain't true. They paid a pittance compared to what they're taking out. People in my generation, and the one before mine, will end up getting far more in Medicare benefits than we ever paid in:
If Medicare costs too much, everyone should be required to share in the pain of cutting it back. There's simply no reason to exempt current seniors.
Except, of course, that it's politically impossible. The "free ride" generation — those of us born just before and just after World War II — will go to our graves convinced that we spent our entire lives working harder than any other generation in history and are now getting back just a small piece of the enormous tax burden we paid in. It's a very comforting little lie, and not one that any sane politician is likely to challenge. It's not just a third rail of politics, it's more like the China Syndrome of politics.