Speculation so far has centered around this Friday as a possible date for announcement of a big move. But no one in the White House has confirmed that timing. But even if the announcement does not come this week, if it comes before Dec. 11, it will greatly increase the risk of a shutdown.
Read MoreRepublicans weigh government shutdown to stop Obama on immigration
Republicans could demand Obama dial back or cancel his order in return for passage of a bill to fund the government. Obama and Democrats could then hold firm and assume Americans will once again blame the GOP for shuttering the federal government, this time in the heart of the holiday season.
The expiring Democratic Senate will not send any measure to the president's desk that would cancel the immigration move so Obama would not have to worry about a veto, at least until the next Congress.
Common sense would suggest Republicans will want nothing to do with this scenario and will thus come up with something that attempts to deny funding to immigration enforcement agencies while funding the rest of the government.
But Democrats may just reject that as well. And the argument that shutdown politics are terrible for the GOP does not hold the kind of weight it once did. Republicans are coming off a giant electoral win in November and believe they have a mandate from voters to fight an unpopular president at every turn.
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Why would newly empowered Republicans want to cave to Obama, especially if he does the one thing that would most outrage their ardent supporters who turned out in November and handed them their largest House majority in generations?
If Obama acts in a sweeping manner, Republicans will have plenty of rhetorical ammunition to suggest the president is acting in an unconstitutional and illegal manner that requires them to use all tools at their disposal to block him. They can even turn the president's words back on him.
Just last year, Obama told Telemundo of efforts to go beyond his legalization of immigrants who came to the U.S. as children: "If we start broadening that, then essentially I'll be ignoring the law in a way that I think would be very difficult to defend legally." In a Google Hangout in February of last year, Obama said of slowing deportations: "This is something that I have struggled with throughout my presidency. The problem is, is that I'm the president of the United States, I'm not the emperor of the United States. My job is to execute laws that are passed."
Those comments will provide powerful rhetorical fodder for Republicans attempting to defend moves to tie government funding to Obama relenting on his immigration actions.
But a shutdown is by no means a certainty. The GOP leadership clearly wants to avoid one and find other means to hammer the president. The White House could decide to hold off on announcing an immigration move until after the lame duck Congress passes a bill funding the government into next year. But even that could just delay a shutdown fight until January or February and keep uncertainty hanging over the economy. And don't forget the debt ceiling will have to be raised in the spring.
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The ideal situation from a markets perspective would be swift passage of a bill in the lame duck to fund the government for the rest of the fiscal year which ends next October. That's not impossible but seems increasingly unlikely. The more likely scenario is a big blow up over immigration that pushes us to the brink of shutdown once more and possible past it.
And the timetable is tight. Congress will likely recess for Thanksgiving at the end of this week and return with just over a week to pass a funding bill. In the interim, Obama could move on immigration. And then the fireworks will begin.