Medicare costs are projected to soar over the next two decades, more than doubling as a share of GDP. This means that anything you put together with Medicare in a sentence will also have explosive growth, such as "Medicare and national park maintenance are projected to more than double as a share of GDP over the next two decades."
For this reason, honest people don't lump together other programs, like Social Security, with Medicare. Social Security's costs are projected to rise at a much more modest pace and, according to the Congressional Budget Office's projections, these added expenses will be fully covered by the Social Security trust fund through the year 2038. But, we don't expect honest discussion from Robert Samuelson.
The problem with Medicare is of course the broken health care system. If the United States paid the same amount per person as people in other wealthy countries then we would be facing long-term budget surpluses, not deficits. While reforming the U.S. health care system is difficult, there are enormous potential gains from trade. However, the Washington elite are such ardent protectionists when it comes to the incomes of their friends in the health care industry, they will not allow the issue of promoting trade in health care to even be considered.
It is also worth noting that the tax plan put forward by Senator Patrick Toomey, which Samuelson touts in this piece, would imply huge tax cuts for the highest income households compared to a situation where the Bush tax cuts are allowed to expire, which is current law.