The perils of Paul Singer's cash for Marco Rubio

Paul Singer GOP's biggest donor
Paul Singer GOP's biggest donor

Marco Rubio got some great news on with backing from influential hedge fund billionaire Paul Singer, who was heavily courted by multiple GOP presidential candidates, including former Florida Gov. Jeb Bush.

But Singer's backing — while a huge positive for Rubio in the money race — does not come without some risks for the Florida senator. Singer is distrusted in the conservative base of the GOP both for his support of same-sex marriage and his support of Rubio's immigration reform efforts in the Senate. According to a person close to Singer, the hedge fund billionaire gave $100,000 to support immigration reform, which the right widely regards as "amnesty" for undocumented immigrants.

Singer's backing encapsulates a major potential problem for the Rubio candidacy. The senator wants and needs the vast piles of money the GOP's Wall Street establishment is capable of pushing his way. Nobody organizes and directs that money better than Singer.

Paul Singer speaking at Delivering Alpha 2015 in New York.
David A. Grogan | CNBC

And knocking out Bush as the economic elite's favorite candidate is a main goal of the Rubio effort. But if he succeeds, Rubio could find himself in the same dilemma as Bush: being the establishment candidate in a party that at the moment loathes the establishment.

Rubio already had a big problem on immigration, though his relatively low standing in the polls masked it from becoming an existential crisis for his campaign. He ran for the Senate as an opponent of "amnesty" for the 11 million undocumented immigrants in the U.S., then championed an immigration reform package with the "Gang of Eight" in the Senate that included a path to legal status that the right regards as amnesty.

Rubio has since disowned his own immigration reform bill though more on procedural than substantive grounds. But with Singer's backing, Rubio will now open himself up to major attacks from Donald Trump and the other strongly anti-immigration voices in the Republican Party. They will be able to more effectively rip him as favoring the elite view of the GOP that wants comprehensive reform with a path to citizenship rather than mass deportations.

Rubio's views on immigration could serve him well in a general election campaign — if he can actually make a clear case for what they are — but they are potentially devastating in the Republican primaries. This is partly why the Rubio campaign has hoped to continue to fly slightly below radar and not peak until much closer to when actual voting begins in January.

They may no longer have that luxury. Rubio is still running well behind Trump and Ben Carson but he is now clearly in third and is emerging as the establishment favorite over a stumbling Bush.

The more he rises, the more fire he will draw from Trump and the conservative media juggernauts led by Breitbart News and the Drudge Report. If conservative media start labeling Rubio as the "pro-amnesty" Wall Street candidate, it could put a serious lid on his ability to move into the top spot should Trump and Carson fade. One person who does not have that problem is Sen. Ted Cruz, who has shown a remarkable ability to hoard cash and position himself to inherit Trump's supporters.

Cruz opposed the "Gang of Eight" bill in the Senate and has embraced the deportation of undocumented immigrants much the way Trump has. Cruz has also taken much stronger stands in favor of using government shutdowns and debt limit fights as tools to force the Obama administration to swallow major spending cuts. These efforts have been largely unsuccessful — and Wall Street views them as highly dangerous to the economy — but they earn Cruz widespread praise on the right.

If the 2016 GOP primary campaign ultimately comes down to a battle between Rubio and Cruz — and it very well may — the U.S. senator from Texas will likely try to paint his Florida colleague as the establishment successor to Bush who cannot be trusted with the nomination.

Rubio has the political skills to deflect many of these attacks and present himself as the better candidate to take on Democratic front-runner Hillary Clinton next fall. And with Singer's help, he will likely have more than enough money to make his case.

But unless Rubio figures out exactly how to package his immigration reform efforts in a way that is palatable to the GOP base, he may wind up with lots of money and establishment support but no path to the nomination.

Sen. Marco Rubio.
Marco Rubio: 'Complete package' or too green?

Correction: Paul Singer gave $100,000 to support immigration reform, according to a person close to Singer. An earlier version misstated the amount.

—Ben White is Politico's chief economic correspondent and a CNBC contributor. He also authors the daily tip sheet Politico Morning Money [politico.com/morningmoney]. Follow him on Twitter @morningmoneyben.