Analysis by Chris Cillizza, CNN Editor-at-large

(CNN) -- Lost amid this will-he-won't-he-sign-it debate over President Donald Trump's decision on the border funding compromise bill is this fundamental fact: If Trump does sign this legislation, it is a massive capitulation by the President on the issue that more than any other animated his 2016 victory.

I can make that point in three very, very simple steps.

Step 1: The key element of the compromise is the allocation of $1.375 billion to build 55 miles of new border barriers.

Step 2: Trump demanded $5.7 billion in dedicated wall funding, shutting down some of the government for 35 days in order to extract that promise from House Democrats.

Step 3: Prior to the government shutdown, congressional Democrats had offered $1.6 billion in wall funding. The White House rejected that offer, insisting that they needed at least $2 billion or $3 billion for the wall to make a deal.

So just in case you missed that, let me summarize: If the President signs this border deal sometime between now and Friday night (when the government is set to shut down again), he will get $200 million less than he could have before the longest government shutdown in history, and $4.325 billion less than he said he needed in order to make good on his campaign promise of building a wall along our southern border.

(Side note: Trump's promise that Mexico will be paying for the wall is, um, not happening.)

To be clear, Trump hasn't said he will sign the compromise deal yet. (CNN has reported, however, that Trump plans to do so.)

"Reviewing the funding bill with my team at the @WhiteHouse!" Trump tweeted Thursday afternoon.

The stark realities of what is in the compromise -- and what's not -- may well be influencing Trump's decision as another shutdown looms: "advisers say Trump has grown increasingly concerned about what's contained in the 1,100-page legislation that was released late Wednesday evening," according to new reporting from CNN.

And every available White House mouthpiece has made clear that Trump isn't thrilled with this final product.

"The President is still evaluating the bill the conference committee has produced," Vice President Mike Pence told reporters in Warsaw, Poland, on Thursday. "He's been very clear that he's not happy with it."

White House press secretary Sarah Sanders sounded much the same sentiment on Wednesday in an interview with "Fox & Friends." "Like the President said yesterday, he is not happy about it, but it is OK. He will get the job done no matter what," Sanders said. "He has alternative options. And he will keep those on the table. We'll see what the final package looks like. The President will make a determination whether or not he is going to sign it."

Desperate to secure Trump's signature on the compromise bill -- due to their fear of the political implications of another government shutdown -- congressional Republicans have adopted this message: The $1.375 billion is just a down payment on the wall! More money to come!

Here's the thing: That's almost certainly not true, at least as it relates to legislative action. Remember that Democrats were willing to play chicken with Trump on a government shutdown over wall funding. And that, at the end of the longest government shutdown in American history, Trump gave in -- agreeing to reopen the government without a single dollar more for the wall. Why, given that history, would anyone think Democrats in Congress are going to give Trump a dime more for wall construction between now and 2020?

It is possible, of course, that Trump uses executive actions to secure money for the wall that is currently sitting in a variety of other pots throughout the government. But, to get to the $5.7 billion he said he needed, he would almost certainly need to dip into money -- $3.6 billion -- allocated to the military by Congress. And to do that, Trump would need to declare a national emergency -- a hugely dangerous bit of precedent-setting that most GOP congressional leaders oppose and that would be vigorously contested in court.

But the most likely scenario is that Trump signs this compromise. He makes sure that everyone knows he is doing so reluctantly. That he doesn't love it. But that he will get his wall money some other way -- without making clear what "some other way" actually is.

Trump has already trotted out that message, in fact. "Was just presented the concept and parameters of the Border Security Deal by hard working Senator Richard Shelby. Looking over all aspects knowing that this will be hooked up with lots of money from other sources," he tweeted on Tuesday, adding: "Will be getting almost $23 BILLION for Border Security. Regardless of Wall money, it is being built as we speak!"

(Nota bene: The wall is NOT currently being built.)

That's all spin, though. The facts here are hard and indisputable: This compromise deal is not only WELL short of the border wall money Trump said he had to have but it's also not even as much as he could have had BEFORE the government shutdown.

Signing this legislation would be a major concession by Trump. On the issue that matters most -- or at least he thinks matters most -- to his base