Hedge-fund billionaire Paul Singer's decision to throw his financial weight behind the donor-class 2016 favorite, 

Sen. Marco Rubio (R-FL)

79%

, has sparked fresh questions about Rubio's coziness with the financial interests funding his career.

Singer was a major financial force behind the Rubio-Obama amnesty and immigration expansion push in 2013.

As Politico reported at the time, Singer "quietly go[t] involved in the fight for immigration reform, making a six-figure donation… to the National Immigration Forum"— a George Soros-backed organization that lobbied for Rubio's legislation to issue 33 million green cards to foreign nationals in the span of a single decade. The announcement of Singer's endorsement highlights an intra-party tension that has emerged with new strength since 

Rep. Paul Ryan (R-WI)

58%