Most Americans haven't been paying much attention to that fact for a simple reason: These shutdown threats seem to arise almost monthly these days and Congress always seems to find a way to kick the can down the road and keep the lights on for another month or two.

After all, there's only been one government shutdown in this century -- 2013 -- and, before that, the last shutdown was in 1995-1996. These things just don't really happen.

Except when they do. And there's some reason to believe that this just might be one of those times -- given the number of moving parts, political calculations and policy differences at work.

Here are five realities about the current debate that aren't likely to change between today and Friday night.

1. There is no DACA/border security deal in play right now

Lost amid all of the coverage of "shithole" coming out of last week's meeting at the White House is the fact that when President Donald Trump scuttled the bipartisan deal built by the Gang of Six there was no plan waiting in the wings to replace it.

That was the deal. The idea that another immigration deal will suddenly emerge sometime over the next 72 hours misunderstands the policy and political complexities at work for both parties here. These deals take weeks and months to come together. And remember that Trump had pledged two days before the immigration meeting last Thursday that he would sign whatever Congress produced on immigration. So there was reason to believe that the deal was done.

2. Trump's "shithole" controversy gives Democrats political cover

The Donald Trump of last Tuesday -- all deal-maker and can't we all get along -- might have made lots of Democrats very nervous about letting the government shut down amid an immigration standoff. But Trump's dismissal of immigrants coming from countries in Africa and central America -- and his preference for immigrants from countries like Norway -- has altered that dynamic.

Suddenly, the debate isn't about Democrats and their views on immigration at all -- it's now centered on whether the President of the United States is a racist. It's a much easier sell for Democrats to go to their constituents now and say, "We tried to make a deal but Trump went off the rails." Much easier.

3. Republicans control all levers of power in Washington

In the two most recent shutdown showdowns -- and, yes, I love that term -- there was split control in Washington. In both the 1995-1996 and 2013 shutdowns, Republicans held Congress while Democrats controlled the White House. That division made the debate over who would be blamed a toss-up in the days leading into the shutdowns. (In both cases, it was Republicans in Congress who bore the brunt of it.)

That is not the scenario that faces us today. Republicans have the White House as well as majorities in the House and the Senate. The idea -- that Trump is pushing via his Twitter feed -- that Democrats will somehow be blamed for a shutdown doesn't seem to be based in any sort of known reality.

"Make no mistake about it, when a party holds the White House and majorities in both the House and Senate, they 'own' any government shutdown," tweeted non-partisan political handicapper Charlie Cook on Tuesday morning. "Things the President has said and done over the last week have only increased the price the GOP has to pay for that ownership."

Polling, too, bears out Cook's point. In a December Quinnipiac University poll , 41% said they would primarily blame Republicans in Congress while 31% said the blame should mainly go to Democrats. Another 16% said they would mostly blame Trump. Add it all up and you find that almost six in 10 people would blame either Republicans or Trump if the government shut down.

4. The Democratic caucus is split between 2018 concerns and 2020 positioning

While Trump's actions over the past week have made the politics of this shutdown showdown (I did warn you I really like that term) simpler for Democrats, the debate over how to proceed on immigration -- and the broader strategic question over how much or little Democrats should cooperate with Trump and Republicans -- is much more complicated for them.

The split within the party largely breaks down along political lines.

The 10 Democrats up for re-election in 2018 in states Trump won in 2016 -- including five in states Trump won by double digits -- are wary of appearing to be reflexively anti-Trump given that many of the voters they will face in November still view the President positively.

On the other side of that divide are the Democrats eyeing the 2020 presidential race -- Elizabeth Warren, Bernie Sanders, Kamala Harris, Kirsten Gillibrand and others -- who know that it's impossible to be too anti-Trump in the eyes of the party's liberal activist and donor base. The view among that group of politicians goes like this: Why should we do any sort of deal on immigration with Trump? If the government shuts down, voters will blame Trump and Republicans. Why capitulate to him in any way, shape or form?

5. It's not clear Republicans have the votes on anything

In the House, at least, Democrats seem very likely to withhold their votes on a clean budget bill that would prevent the government shutdown. If that happens, it's not clear that Speaker Paul Ryan has the votes -- or can get them -- among the GOP conference for a(nother) short-term budget plan.

The House Freedom Caucus -- the most conservative element within the House GOP -- is making rumblings that they may not be willing to provide any (or very few) votes for another kick-the-can move. If the Freedom Caucus comes out against another effort to fund the government in the near term, then Ryan will have to either a) prepare for the shutdown or b) find Democratic votes somehow.

In short: Don't assume Republicans can simply fund the government at the last-minute on Friday night. They may not be able to.