And the president’s long-hidden tax records, obtained by The New York Times, also reveal this: how he engineered a sudden financial windfall — more than $21 million in what experts describe as highly unusual one-off payments from the Las Vegas hotel he owns with his friend the casino mogul Phil Ruffin…

The new findings, part of The Times’s continuing investigation, cast light on Mr. Trump’s financial maneuverings in that time of fiscal turmoil and unlikely political victory. Indeed, they may offer a hint to one of the enduring mysteries of his campaign: In its waning days, as his own giving had slowed to a trickle, Mr. Trump contributed $10 million, leaving many people wondering where the burst of cash had come from.

The tax records, by their nature, do not specify whether the more than $21 million in payments from the Trump-Ruffin hotel helped prop up Mr. Trump’s campaign, his businesses or both. But they do show how the cash flowed, in a chain of transactions, to several Trump-controlled companies and then directly to Mr. Trump himself.

The bulk of the money went through a company called Trump Las Vegas Sales and Marketing that had little previous income, no clear business purpose and no employees. The Trump-Ruffin joint venture wrote it all off as a business expense.