I think I mentioned this at some point, but I keep reading things that don't seem to get it, so a quick dedicated post about the flexibility of the fiscal year deadline.
Yes, the deadline for funding the government is a hard deadline. No CR, and the government shuts down. The deadline is the end of September.
However, one thing that Dylan Matthews didn't include in his nice explainer this morning): just as Congress can pass a one-year CR or a ten week CR (what the GOP is apparently planning for now), they can also pass a one day or ten day CR. Any length of time at all, in fact. Hours, if they want. So if we get to the end of the month and they haven't all figured it out, there's nothing at all to stop the House from passing, and the Senate from agreeing to, a little more time for figuring it out.
Of course, it has to pass. Which means it would have to be as "clean" as possible -- certainly the Democrats in that situation would not sign off on a one week defunding of the ACA, for example. So it's not clear whether a House that refused to pass a clean ten week CR would be willing to go for a clean ten day CR, and in general if one side thinks that a short negotiating extension isn't in their interest, then it won't happen.
But it can. And anyone gaming out the next couple of weeks should remember about that option, especially if they believe that simply running out of time is a significant factor in a shutdown.