Billionaire donor backs Rubio for US president: NY Times

One of the wealthiest and most influential Republican donors is throwing his support behind the presidential campaign of U.S. Senator Marco Rubio of Florida, the New York Times reported on Friday.

SEE MORE: Marco Rubio on Jeb Bush: 'I still have tremendous admiration' for him

Billionaire New York investor Paul Singer sent a letter to dozens of other donors on Friday declaring his support for Rubio in a major blow to the struggling campaign of former Florida Governor Jeb Bush, the newspaper said. They are among the candidates seeking the 2016 Republican presidential nomination.

Rubio, Bush, New Jersey Governor Chris Christie and several other Republican candidates had eagerly sought Singer's support, the Times said.

SEE ALSO: AP-GfK Poll: Republicans prefer an outsider candidate

In the letter, Singer described Rubio as the only candidate who can "navigate this complex primary process, and still be in a position to defeat" Hillary Clinton, the front-runner for the Democratic presidential nomination in the November 2016 general election.

Singer gave more money to Republican candidates and causes last year than any donor in the country, the Times said, citing the Center for Responsive Politics.

See Rubio out on the campaign trail:

He is courted by Republicans both for his willingness to give and for his network of fellow conservative donors, the newspaper reported.

The Times did not say how much Singer intended to donate to Rubio, who is coming off a strong debate performance on Wednesday night in Colorado.

Rubio is third behind businessman Donald Trump and retired neurosurgeon Ben Carson in a Real Clear Politics average of national opinion polls for the Republican race.

SEE ALSO: Donald Trump lashes out at media after 3rd GOP debate

Bush, who is in fifth place in the polling and recently downsized his campaign staff, gave what is widely viewed as a lackluster performance in the debate.

For more on the 2016 presidential race, see the Reuters blog, "Tales from the Trail" (here)

(Reporting by Eric Beech in Washington; Editing by Will Dunham)

More on AOL.com:
1 dead, 1 hurt in collapse at midtown building
US to deploy special operations forces in Syria: Official
This map shows how large Europe's refugee crisis really is