It could also mark Day 1 of a government shutdown if Congress doesn't pass a spending bill authorizing funding, or if the president doesn't sign it before then. This is a risk the GOP will be eager to avoid, although in recent days chatter has again picked up as a result of Trump's insistence to add wall funding in the spending bill. As noted earlier today, there is virtual unanimity among Democrats to oppose any bill that budgets for a wall, and since passing a new Continuing Resolution would require 60 votes in the Senate, at least some Democratic support is needed.
So while it remains at best a moderate risk factor - Goldman's latest estimate puts it at about 1-in-3 chance - the question of what happens if the government does shut down at midnight on Saturday is starting to percolate. Here are some thoughts from Citi.
First, threats of a shutdown are more common than actual shutdowns. The last one occurred in October 2013, and the one prior to that was 1995/96. Those that last have an impact on the economy. In 1995/96 the government shut down for 21 days. In 2013, for 16 days. But not all shutdowns are impactful. During the Regan administrations, there were a total of 8 shutdowns with the maximum lasting 3 days.