Donald Trump has just been caught in another lie. This is news, but it's hardly shocking, since he's been caught in so many lies it's tough to even keep count of them all. In fact, it'd be a lot easier to tally up the promises Trump has made that didn't turn out to be lies. If there are any, that is.

Today the Washington Post revealed that Trump's grandiose new ballroom has been planned all along to cost the taxpayers a huge amount of money. Trump promised -- over and over again -- that "not one thin dime" of taxpayer money would be used for the project, but now it appears that a whopping three billion dimes will be required from the public treasury.

The price for Trump's monument to tastelessness has kept going up and up, pretty much ever since he announced it. At first, it was supposed to cost $200 million. That was quickly upped to $300 million and then $400 million -- which Trump kept insisting was going to be completely privately funded. At the end of March, Trump repeated this lie: "This is taxpayer-free. We have no taxpayer putting up 10 cents." Which was nothing more than a big, fat lie, as the Post reports today:

But a detailed project summary prepared for the White House by the contractor more than three weeks before Trump's comments estimated the total construction cost at $600 million -- with more than half coming from taxpayers, according to a copy of the contractor estimate obtained by The Washington Post.

By the time Trump made his comments in March, the federal government had already approved more than a dozen payments to the contractor overseeing the work, Clark Construction, totaling tens of millions of dollars in public funds, according to a log of the contractor's invoices obtained by The Post.

. . .

Multiple project summaries provided to the White House by Clark Construction show that internal cost estimates have been significantly higher than administration officials have acknowledged in public comments or court filings. They also show that the work was projected to rely heavily on taxpayer dollars from the moment it was announced.

Got that? Trump planned on using taxpayer money from the very start and he just hoped nobody would notice. This even, rather brazenly, included taxpayer money to tear down the East Wing:

White House officials received a preliminary estimate, dated July 11 [of last year], projecting that construction would cost $270 million, with over $100 million coming from taxpayers through the Secret Service and the White House Military Office, the records show.

Emails from that time show that administration officials planned to use $3.6 million of Secret Service money to cover initial expenses for site preparation before demolition.

. . .

More than $1.6 million in Secret Service funds was also budgeted to cover part of the demolition itself, according to a cost estimate.

How does "tearing down part of the White House" qualify as something the Secret Service should pay for? It boggles the mind. But even these amounts would soon be dwarfed by the ever-rising costs for the project:

By March, Clark had informed the White House that the projected cost had increased to $600 million. A project summary dated March 5 shows that nearly half of that, $293 million, was expected to come from "private sources." The estimate said an additional $155 million would come from the Secret Service, $149 million from the White House Military Office and $3 million from the Executive Residence, all sources funded by taxpayers.

So over half of the budget -- more than $300 million -- is going to come from taxpayer money. As stated, that is over three billion dimes... and counting.

This is pretty obviously why Republicans in Congress tried to sneak a $1 billion slush fund into a budget bill that Trump could use to cover the ballroom's cost. Even some Republicans balked at this, and the measure was stripped out of the bill which eventually did pass -- but it shows that at least some in Congress were aware that Trump's pledge that it would all be constructed with private funding was nothing more than a lie.

The ballroom has always been a favorite pet project for Trump. He can feel like a real estate guy once again, with the sounds of construction echoing through the White House grounds. He reportedly spends an inordinate amount of time overseeing the details of the project -- time he's not spending on solving any of America's pressing problems.

But his fantasy ballroom was never a priority for his base. Trump never really campaigned on the idea -- probably because he knew it wouldn't be a winner for him. And the polls reflect this. The Post ran a poll a few months ago and it showed Americans were against the ballroom project by a 2-to-1 margin (56 percent opposed to 28 percent support). Democrats opposed the project 87 percent to 4 percent. Even 20 percent of Republicans were against the idea. Independent voters disapproved by more than a 3-to-1 margin (61 percent opposed to 18 percent support). All of those numbers were taken before the public knew that they'd be picking up half the inflated tab for the project, it bears mentioning.

The news that Trump was caught in another lie will probably be greeted by most of the public with some version of: "Oh... must be another day ending in a 'Y'...." But it is also a valid political bludgeon for Democrats, since the project is so widely unpopular to begin with. Democratic candidates already routinely mention Trump's ballroom while talking about the affordability crisis, because it is so easy to do: "Donald Trump doesn't care what the cost of groceries is for your family because he's too busy building a glorious ballroom that you'll never set foot in." Now all they have to do is add the fact that American taxpayers will be picking up over half the tab for this gargantuan monument to one man's outsized ego.

Again, this will be quite easy to do. Just find a few clips of Trump promising "not one thin dime of taxpayer money" will be used (there are plenty to choose from), and then run a giant screamer headline over it stating: "THREE BILLION OF YOUR DIMES WILL BE USED." Or maybe preface that with: "TRUMP LIED." The public already thinks Trump (and by extension his fellow Republicans) are woefully out of touch with the problems they face, and this will just drive that point home in a big way.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant