Donald Trump should put his money where his mouth is.

The real estate mogul says he's worth 'in excess' of $10 billion. I think he's lying, as does pretty much every expert and financial journalist who has looked into the question. Forbes has put his net worth at $4.5 billion. Bloomberg says it's below $3 billion. Billionaire Mark Cuban has cast doubt on whether Trump is even a billionaire at all.

I've read the analyses, but common sense always told me he was full of it. Actual multi-billionaires tend not to waste their time recording videos hawking steaks in the Sharper Image catalog. They don't bother with snake oil schemes peddling dietary supplements. They don't claim under oath that much of their net worth depends on how good a mood they're in. And they don't threaten to sue anyone who suggests they aren't as rich as they claim.

This last point is especially significant. Trump's business model is to exploit his brand as a super-successful Manhattan real estate mogul. The fact that he is, in reality, a 'relatively minor player' in that world, as economics writer Adam Davidson recently noted in the New York Times Magazine, is entirely beside the point. He's selling the sizzle, not the steak (clearly, not the steaks).

That's especially true overseas, where he does a large share of his business (he's in Scotland for some grand opening right now). He's nowhere near the richest man in America, but he's arguably the American most famous for being rich. That opens doors in Eastern Europe and Asia. It also improves his mood, which apparently can be a real windfall.

I've talked to numerous political pros and quite a few actual billionaires, and the totally uncorroborated theory most of them hold is that Trump never expected to do this well. It was a P.R. stunt that got out of hand. The dog caught the car and now he doesn't know what to do with it.

Circumstantial evidence for this can be found in Trump's latest fundraising report. It was, by any objective measure, a disaster. I wouldn't be surprised if RNC Chair Reince Priebus reacted to it the way that German guy did when he looked inside the Ark of the Covenant at the end of the first Indiana Jones movie.

In short, the alleged decabillionaire's campaign is broke. In May, which should have been a boffo fundraising month, the campaign raised $3.1 million (Mitt Romney during the same period had raised $78 million). The Trump Train went into the crucial month of June with just under $1.3 million cash on hand. That is a pretty good number — for a congressman. Only 78 representatives and 43 senators have more cash on hand than the GOP's presumptive nominee.

Perhaps more tellingly, the failed steak and vitamin mogul spent nearly a fifth of the money he raised on his own businesses and salaries for himself and his family. One of his biggest outlays was renting out the Mar-a-Lago club — which he owns. Odd.

During the primaries, Trump routinely insisted that he was turning down millions in donations from fat cats eager to board the Trump train. 'The week before last, a lobbyist … offered $5 million, 'Please. I want to give you $5 million for the campaign,' ' Trump recounted to reporters last August. 'I said 'I have no interest in taking that.' In fact, I think it's the first time he's ever been turned down.'

That was back when Trump's was the great self-funder. But he changed his mind a while ago. He wants help now, but it's not forthcoming.

It seems strange that all of those super-rich friends would be eager to donate during the primaries but now have empty pockets. Perhaps such offers never happened. Or, maybe, no one wants to hand money to a guy who insists he could easily self-fund the whole thing with a fraction of his alleged wealth.

And that's the thing. If Trump's worth $10 billion, spending $1 billion is no great sacrifice. He could still cover the bills for his private jet. OK, maybe he'd have to sell something. Is that really too much to ask? The founders pledged their lives, their fortunes and their sacred honor. Surely he could pawn Trump Tower.

So, I ask you, Mr. Trump, just do it already. Put your money where your mouth is. You say you're the only one who can save America. Henry IV said, 'Paris is well worth a mass.' Surely America is worth a tenth of your alleged fortune.

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