When we outlined why the key date is October 17, we noted the ebb and flow of the Treasury. On any given day, money from income and corporate taxes and other sources flows in; money moves back out to pay bills. Treasury Secretary Jack Lew estimates that the the 17th will be the first day on which the amount we bring in, combined with the amount we have on hand, will be insufficient to pay off the bills that come due. Goldman Sachs, which for obvious reasons is watching this closely, suggests that there's a little more time than that before things start getting really rough. But if we can't borrow more money, bills will come due that we can't pay.

So the question is: Can Treasury choose to pay some bills before others? Could it, for example, choose to hold off on paying soldiers so it could pay off the interest on its existing loans (keeping those financial markets happy)? As our colleague Matt O'Brien at The Atlantic noted last month, even this would have a devastating effect on the economy, but could allow the government at least some room to maneuver if a debt ceiling increase could happen quickly. For the soldiers and elderly and employees and so on that rely on those payments, this would of course be devastating. "[C]utting 32 percent of federal spending overnight would certainly make things look real grim real fast," O'Brien wrote. "Indeed, that much austerity would cost us millions of jobs at an annualized pace." (Still from a sailor surprising his grandpa via YouTube, above right.)

Second: Banks

O'Brien also points out that banks rely on short-term borrowing to pay bills. When the government flirted with default during negotiations over the debt ceiling in 2011, interest rates for doing so spiked dramatically, meaning that the cost of such loans for banks increase as well. Vastly higher costs for banks on routine activity has obvious repercussions in the broader economy.

Now, keep in mind, both of those things are in the best-case scenario in the event Congress doesn't raise the debt ceiling. If the Treasury can prioritize how it pays its bills, ignoring some of them, this is what would result.

But as Business Insider points out, Treasury probably can't do that. There is "no legal basis" for choosing to take care of its interest payments before SEAL Team Six. But moreover, it would require jerry-rigging some way of dividing up its millions of daily transactions in order to only pay those bills that were least likely to make the snowball of economic calamity grow bigger. It's safe to assume, then, that everyone would suffer at once, even if in the best case everyone suffers eventually. (Photo of JPMorgan Chase chair Jamie Dimon via Associated Press, above right.)

Third: Holders of government debt

Next to feel the pain (well, probably simultaneously, really) is those to whom the government owes interest payments on debt and bonds. At some point, they're likely not to get paid. Even in the best-case scenario, there will be days on which there isn't enough money to pay even the high priority recipients as Business Insider points out. So the negative effects of having at least some Treasuries go into default are almost certain.