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Rubio scores major endorsement from billionaire GOP donor Paul Singer

Republican presidential candidate Marco Rubio speaks at an event in Sioux City, Iowa, on Oct. 30, 2015. (REUTERS/Mark Kauzlarich)

ORANGE CITY, Iowa -- Republican presidential hopeful Marco Rubio picked up a major endorsement from one of the most influential -- and wealthy -- donors, billionaire hedge-fund manager Paul Singer.

The endorsement caps a strong week for Rubio in which he was widely seen as the standout candidate in Wednesday's GOP debate in Denver.

Singer is one of the most influential money players in the GOP – not only because of the large sums he personally donates, but because he has helped organize a network of like-minded wealthy contributors that is a significant power center within the party.

The nod from Singer was confirmed by an aide to the Rubio campaign and it was first reported by the New York Times.

"When people donate to us, they're buying into our agenda and I'm glad that he has," Rubio said from Northwest Iowa on Friday night. "It'll help us with resources."

But, he added, "resources alone are not enough."

"You have to have the right ideas and the right principles," Rubio said.

In a letter to Republican donors, obtained by the New York Times, Singer said that Rubio's optimistic message and sure-footedness swayed his decision.

“He is accustomed to thinking about American foreign policy as a responsible policy maker,” Singer wrote. “He is ready to be an informed and assertive decision-maker.”

Throughout the year, Singer and his allies have hosted private listening sessions with many of the 2016 GOP candidates, who have assiduously courted the hedge fund manager.

Singer is worth an estimated $2.1 billion, according to Forbes. Securing his endorsement means Rubio now has one of Mitt Romney’s biggest financial backers on his side. Not only was Singer one of Romney’s most prolific fundraisers, but he also contributed $1 million to a super PAC supporting Romney’s candidacy.

A supporter of gay marriage, Singer has sought to use his wealth to push the GOP to embrace gay rights. In the 2014 congressional elections, he was the third-biggest donor to independent political committees, doling out $10.6 million to an array of super PACs, according to the Center for Responsive Politics. A third of that money went to American Unity PAC, a group that supports pro-marriage equality Republicans.

He is also a staunch supporter of Israel, serving on the board of the Republican Jewish Coalition.