Here's the better question: If you were serious about reducing the deficit, what would you cut?

It should be possible to reduce Medicare costs significantly by going after healthcare costs in general, i.e. create a ton of new medical residency slots and train a lot of new doctors, and make the healthcare companies actually compete with each other. The AMA and healthcare companies are going to fight you hard.

We currently make large social security payments to affluent retirees who paid in less than we're paying them out. We could reform the system to cost less, i.e. not pay out as much to people who don't need the money. The AARP isn't going to like it.

The DoD budget is pretty big and a lot of it is waste or corruption. But to do this well you have to be good at identifying which parts, you still can't eliminate all of it because some of it is pretty important, and this one is the smallest of the three. And the defense contractors will try to stop you.

To make a meaningful dent in the deficit you would have to do at least two of those but no one is willing to do any of them.