Paul Singer, founder and president of Elliott Management, is seen July 15, 2015. David A. Grogan/CNBC/NBCU Photo Bank via Getty Images

Billionaire New York investor Paul Singer, one of the wealthiest and most influential Republican donors in the United States, is now supporting Florida Sen. Marco Rubio's candidacy for the Republican Party's 2016 presidential nomination. The move is a major blow to the candidacy of a fellow Republican, former Florida Gov. Jeb Bush, the New York Times reported Friday.

Singer described Rubio as, “the best explainer of conservatism in public life today, and one of the best communicators the modern Republican Party has seen. Marco Rubio can appeal to both the head and the heart,” in a letter sent to dozens of other donors Friday that was obtained by the New York Times. Singer also touted Rubio’s optimistic message about America’s future, his work on the Senate Foreign Relations Committee and his skill in making a convincing case to voters as key reasons for supporting him, the Times reported.

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

Last year, Singer reportedly gave more money to Republican candidates and causes than any other donor in the country, and Republican candidates Bush and New Jersey Gov. Chris Christie have aggressively competed for his support. Singer was a top donor for Bush’s brother, former President George W. Bush.