A couple weeks ago the Government determined that Healthcare would be 20% of our GDP by 2017.  That means in nine years one out of every five dollars generated by Americans is going to go to Medicare and Medicaid and private health insurance.
Our government budget now is about 20% of our GDP.  MnM costs about 5% of the GDP, just a little bit less, and Social Security takes about 4.2% of the GDP.  So combine the two and you have almost half the budget, 10% of GDP, going to Social Security and MnM.  All of these three expenses are called "Mandatory Spending" because, unless Congress votes to change it, they are automatically spent by the government.  That makes things easier for the government to run.  It also makes it harder to change these programs because, unless you have 60 Senators behind a change, you will inevitably have a crushing filibuster.
Now factor in that Healthcare costs including Medicare and Medicaid are rising in excess to the GDP (meaning our country's economy is growing at a slower rate than our health care costs) and that our population is aging (and disproportionately aged - hello baby boomers) and you have a serious problem.  Social Security will rise from 4% of the GDP to 6% of GDP.  That does not sound too bad, after all 4 - 6 is only a 2% increase.  However that 2% increase is 1) an increase of 50%, which means the payroll tax will be adjusted so it generates 50% more revenue, and 2) that 2% increase is distributed over fewer workers - as the boomers age we have less workers to replace them in the workforce so the tax burden is distributed to fewer people.  Keep in mind the payroll tax is regressive - it has an earnings ceiling, the taxation stops at about $90,000, so the tax increase will be forced onto the lower and middle income groups.
Medicare and Medicaid and Social Security costs will be account for 26% of our GDP in nine to fifteen years.  Meanwhile our debt from the poorly run Iraq war (I am not saying whether or not I support it I will cover that later but I am going to say it has been poorly managed monetarily speaking), our debt from other government programs, and our debt from United States citizens over-spending and needing to borrow is going to put such a huge, enormous, and spectacular debt burden on us in ten years that we could very well be buried up to our eyeballs in Iou's and still need even more money just to finance the government.  Our style of life could be drastically different due to the amount of debt we have. 
As for MnM by 2030 to 2050 they will total 20% of the GDP by themselves if we do not change anything. So add in Social Security, and 26% of our GDP will be spent on just those three things.  1 out of every 4 dollars going to the government (assuming we are not going to borrow).

I will evaluate the Obama, Clinton and McCain's approach (or lack of) to dealing with the upcoming fiscal crisis soon - but in the meantime I want y'all to realize that you have a choice in this election and that only one of these candidates is going to address the fiscal crisis so that we have the best chance of coming out of this ok.