In theory, the deadline for avoiding a government shutdown is 11:59 p.m. Sept. 30. That gives Congress seven days to figure something out. But those seven days are, at this point, pretty much spoken for.

Harry Reid has a hard job. (Photo by Alex Wong/Getty Images)
Harry Reid has a hard job. (Photo by Alex Wong/Getty Images)

The Senate is now considering the House's continuing resolution, which defunds Obamacare. But Republican Sen. Ted Cruz, among others, has promised to filibuster that bill. So, here's what happens next:

1) The Senate files cloture on the motion to proceed to the bill. A "cloture" vote -- which is how you overcome a filibuster -- takes two full calendar days. So that takes us to Wednesday.

2) There are 30 hours of post-cloture debate. If Cruz and his compatriots choose to burn time -- and they probably will -- that means it'll be Thursday before the Senate is actually on the bill.

3) The Senate files cloture to move to a vote on the bill and the amendment stripping out the "defund" language, as Majority Leader Harry Reid has pledged. Two more calendar days. Now it's Saturday.

4) Another 30 hours of post-cloture debate. Now it's Sunday. Finally, the actual vote can happen.

5) The Senate sends the bill back to the House. That'll probably happen on Monday, Sept. 30.

The key is what happens after that. The House could just pass the Senate's CR and send it to the president. If that happens, no shutdown. But if they don't want to pass the Senate's CR -- which won't defund Obamacare or offer any new concessions to House Republicans -- there's no real time left to send a new bill back to the Senate. "If that happens," one Senate aide told me, "I think we just go to shutdown."

Now, it's possible for the Senate to act quickly, if all 100 senators agree to act quickly, but Cruz, et al have shown no inclination of being willing to act quickly on anything that doesn't defund Obamacare. To believe there could be some rapid-fire exchange of compromise bills on Sept. 30 means believing that Cruz and Sens. Rand Paul and Mike Lee and others agree to abet the exchange.

At this point, I think it's likely we avoid a shutdown because the House agrees to the Senate's CR. But it's entirely possible that we could have a shutdown just because there isn't time to work out a deal that averts one.