Billionaire New York hedge fund investor Paul Singer has thrown his support behind US presidential candidate Senator Marco Rubio.Rubio, the Republican senator from Florida, is the only candidate who can “navigate this complex primary process, and still be in a position to defeat” Hillary Rodham Clinton in the November general election, Singer said in a letter sent to dozens of his friends and fellow Republican donors, the New York Times reported over the weekend. Singer gave more money to Republican candidates and causes last year than any other US donor, according to the Times.Rubio made a strong showing in last week’s debate in Colorado among candidates seeking the Republican nomination for president. Several Republican candidates were vying for Singer’s support.Singer, in his politics, is extremely pro-Israel and a proponent of same-sex marriage. He is on the board of the Republican Jewish Coalition and a major donor to The Israel Project. He is known for buying the debt of sovereign countries and then seeking full payment, including Peru, the Congo and Argentina. Argentine President Cristina Fernandez de Kirchner has called him a “vulture.” She has linked Singer’s money with efforts to prevent Argentina from signing a memorandum of understanding with Iran on jointly investigating the AMIA bombing, which killed 85 and injured 300. The memorandum, which has received international criticism, was signed in January 2013.Forbes puts Singer’s net worth at $2.1 billion.