(CNN) President Donald Trump -- and his associates -- have given all sorts of reasons for his refusal to release his tax returns: He's under audit! Voters don't care! His taxes are too complex for regular people to understand!

None of those reasons made -- or make -- any sense. But now, thanks to CNN reporting , we may know the real reason why the President is fighting so hard to keep his returns from ever seeing the light of day: Because he paid so little in taxes -- especially for someone who makes as much money as Trump does.

"He thought he could defend the return," former Trump associate Sam Nunberg told CNN's Vicky Ward of a conversation he had with Trump in 2013. "I inferred from the conversation that he believed that it was a low number and he'd look savvy." Added Ward in the piece: "A second person, a former senior adviser to Trump, who also joined them for lunch that day, recalls Trump being enthusiastic about releasing his returns for this reason."

Which is very interesting! And comports with things Trump has said publicly!

In the first general election debate of the 2016 campaign , Hillary Clinton pushed Trump on his lack of transparency on his taxes. And this exchange occurred:

CLINTON: "So you gotta ask yourself -- why won't he release his tax returns? And I think there may be a couple of reasons. First, maybe he is not as rich as he says he has. Second, maybe he's not as charitable as he claims to be. Third, we don't know all of his business dealings but we have been told through investigative reporting that he owes about six hundred and fifty million dollars to Wall Street and foreign banks. Or maybe he does not want the American people, all of you watching tonight, to know that he has paid nothing in federal taxes because the only years that anybody has ever seen for a couple of years where he had to turn them over to state authorities when he was trying to get a casino license. And they showed he did not pay any federal income tax.

TRUMP: "That makes me smart."

Later in that same debate, in response to Trump bashing the government for doing little to bolster the country's infrastructure, Clinton said this: "And maybe because you have not paid any federal income tax for a lot of years." To which Trump replied: "It would be squandered too, believe me."

Which sure seems like an admission that he hasn't paid a whole lot of taxes, right?

Here's what we do know about Trump's taxes -- thanks to reporting by The New York Times, among others : On his 1995 tax return, Trump declared a loss of $916 million -- a move that could have allowed him to avoid paying taxes for almost the next two decades. Under IRS law, any business can avoid paying taxes in a given year if it lost money in the previous year.

So, if Trump did indeed pay no taxes for almost 20 years, you could see why that's the sort of thing he wouldn't want to be made public before he runs for a second term. Because what might have been smart for Donald Trump, the private citizen, looks a lot worse for Donald Trump, the president. Especially since Trump has routinely railed against companies taking advantage of the tax code to avoiding paying any taxes at all.

"Only fools, or worse, are saying that our money losing Post Office makes money with Amazon," Trump tweeted in April 2018 . "THEY LOSE A FORTUNE, and this will be changed. Also, our fully tax paying retailers are closing stores all over the country...not a level playing field!"

There are, of course, other possible explanations here. Trump isn't nearly as rich as he says he is. He didn't give any money to charity. But the one that jibes most with what Trump has said publicly -- and privately, according to Nunberg -- is that he worked every possible loophole to pay as little in taxes as he could.

Hypocrisy would be nothing new for Trump. But gaming the swamp to feather your own nest? That runs directly counter to Trump's image among his base as the one honest man in all of Washington.