There is a real debt limit.

Some things even with the worst of intentions are impossible. Bernie Sanders by way of promising free college and free healthcare is pushing the limits of the possible. Supposedly free healthcare would be financed in part by a new payroll tax meaning of course it's not free unless you pay no taxes. The free college is dependent upon a tax on Wall Street speculation whatever that maybe but there exits among his supporter the idea that if the new taxes do not cover the expenses he can merely increase the national debt to breaking point.
That idea may have worked for sometime even as late as the year 2000 but today there is a limit to available credit. In addition to the aforementioned taxes as of late the Sanders people have added a new fix to the insanity. Bernie would raise the maximum tax rate to 73%. We don't need John Maynard Keynes to tell us that raising the tax rate does not necessarily raise revenue. With an economy limping along at a 0.7% annual growth rate even a modest tax increase is certain to produce a recession which means people would earn less and pay less in taxes. The same is true of the other two tax measures but the payroll tax, because it would be unavoidable for most taxpayers, is the real killer. Sanders seem to think wealth is something people keep stacked up in their basements like so much firewood. Take a few sticks and no one except the taxed individual will know the difference. That would be true of a gold hoarder but most people keep their money in banks. The more that is taken out of depositor accounts the less the bank has to lend for mortgages or business investments. As a result carpenters, electricians and plumbers are not hired to build homes nor are cooks and waitresses whose would be employer could not get a business loan to open a restaurant. Now because of the tax increase carpenters, electrician, plumbers, cooks and waitresses are not paying taxes but are instead collecting unemployment benefits and food stamps.
So just borrow the money and let the next president worry about it. After all there is long history of deficit spending. There are various estimates of the cost of a Sanders presidency but a frequently cited estimate predict that it would cost $18 trillion over 10 years. A little research provided a vivid comparison. On January 26 of this year the market cap, that is the intrinsic value, of the entire Standard and Poor 500 was $17.5153249 trillion. In other words Sanders would burn through the wealth of the 500 largest companies in the US every 10 years. Yes, Amazon and Face Book grew to be great in a hurry but other companies such as Dupont, which began by selling gun powder during the Revolutionary War, have spent hundreds of years to get where they are today.
This of course begs the question who do you see about borrowing $18 trillion? Presently about 60% of the US debt is held domestically and much of that is by the government itself. Social Security is required by law to place its funds into government bonds and the Federal Reserve is a major debt holder but what entity either in the US or in the nearly bankrupt global economy could purchase an additional $18 trillion every 10 years? As wealth is finite so is the ability to borrow. At some point there exists a real and absolute debt limit.  Is it more than just coincidence that Mr. Sanders' initials are BS?