Republican presidential candidate Donald Trump listens as Treasure Island owner Phil Ruffin, right, speaks in Des Moines, Iowa. At left is Ruffin's wife, Oleksandra Nikolayenko. (AP/Andrew Harnik)

Casino mogul Phil Ruffin, a longtime friend and business partner of Donald Trump, gave $1 million last year to a super PAC supporting the real estate tycoon's presidential run, just two weeks after the group was formed.

The seven-figure contribution from Ruffin, who owns the Treasure Island Hotel and Casino in Las Vegas, made up the bulk of the $1.74 million that the Make America Great Again PAC raised before shutting down, according to new documents filed Wednesday with the Federal Election Commission.

The super PAC closed up shop in October after The Washington Post reported on multiple ties between the organization and Trump's official campaign. Campaign manager Corey Lewandowski told The Post that the group was not sanctioned by the Trump campaign. But Trump attended at least two events for the group, and his daughter's mother-in-law gave it $100,000.

Make America Great Again eventually refunded Ruffin's money and a few other contributions in December after spending about half a million dollars on consulting, legal expenses, travel, polling and other costs, the filing shows.

[Trump campaign ups its payments to firm of super PAC operative]

Trump and Ruffin have been close for 18 years. Last summer, Trump floated Ruffin's name as someone he would send to negotiate with China if he were elected president, a comment Ruffin said later was a joke.

The men are "50-50" partners in Las Vegas' gold-gilded Trump International Hotel, and Trump was the best man at Ruffin's 2008 wedding, according to Michelle Knoll, senior vice president of communications for Treasure Island.

"They are best friends and business partners, and when Mr. Trump spoke about running, Mr. Ruffin said, 'I’ll give you $1 million,'" Knoll said. "Trump said he didn’t want the money."

Nevertheless, Ruffin went ahead and made the contribution to Make America Great Again on July 16, 2015 — two weeks after the super PAC filed its initial paperwork with the FEC. Knoll said she did not know who solicited the donation or how Ruffin learned about the group.

Last week, Ruffin joined Trump at a rally event in Des Moines, which Trump organized after deciding to boycott Fox News' Republican debate. There, Trump singled out the Treasure Island owner for making another $1 million donation — this one to support veterans' groups that Trump said would benefit from money raised at the event.