WASHINGTON — Some of the biggest donors and fundraisers in the Republican Party, still uncertain who should get their support in 2016, are sprinkling their money around a presidential field that grows by the day.

The largesse born of their indecision has a notable exception: Rand Paul.

The Kentucky senator has aggressively tried to raise money around his effort to curtail the surveillance powers of the National Security Agency, emailing supporters and posting messages on social media imploring people to “celebrate this victory” with their cash.

In doing so, he’s exacerbated the perception among some of the GOP’s most generous donors that his positions on foreign policy make him an unacceptable choice for the White House. This is especially so to those who consider an aggressive posture abroad and support for Israel paramount.

“I do not know of a single person in Mitt Romney’s donor network who will be with Rand Paul,” said Phil Rosen, a Manhattan attorney and top fundraiser for the 2012 Republican nominee. Rosen said he met with Paul and politely told him he wouldn’t be supporting him “because of his isolationist and libertarian policies.”

Rosen hasn’t settled on his choice in next year’s primary contest but expects to decide soon from a short list. Other prominent donors are doing the same, with some willing to give money to multiple candidates in the early stages of the campaign, but not to Paul.

Among them: Las Vegas casino owner Sheldon Adelson, New York hedge fund pioneer Michael Steinhardt and Ken Abramowitz, founder of a venture capital firm in New York. All three have given money to South Carolina Sen. Lindsey Graham, who announced his presidential campaign on Monday by saying he wants “to be president to defeat the enemies trying to kill us.”

“Graham in particular has a terrific record in Congress and is experienced and articulate,” said Steinhardt, who is also giving to former New York Gov. George Pataki and former Arkansas Gov. Mike Huckabee.

The weight of donor opposition to Paul hit his campaign soon after he launched it in April, when a politically active nonprofit, the Foundation for a Secure and Prosperous America, began a $1 million television advertising campaign against him in the four early primary states. The nonprofit can raise unlimited money and is not legally required to disclose its donors.

Several other groups are prepared to pounce on Paul if they sense he is gaining traction in the race. Among them is a group led by John Bolton, a former ambassador to the United Nations who recently decided against running himself, but plans to push for strong national security policies from the sidelines.

“I’ve spoken to well over 1,000 major Republican donors and can remember only one who agreed with Rand Paul on foreign policy,” Bolton said. “The views he represents are a tiny, tiny minority within the Republican Party.”

Unlike several of the other Republican candidates for president, Paul doesn’t have an obvious billionaire — or group of billionaires — backing his campaign, as New Jersey Gov. Chris Christie does with Home Depot founder Ken Langone and Florida Sen. Marco Rubio does in car dealer Norman Braman.

Campaigning in South Carolina last week, when he spoke about his fight against renewing the NSA’s authority to collect Americans’ phone records in bulk, Paul said he isn’t concerned about the big donors lining up against him. But he said he wouldn’t turn down their money.

“If you know some billionaires, and you want to send them our way, we’re happy to talk to them,” Paul said. “It’s more about votes than it is about dollars, and I think we’re going to have plenty of money to compete.”

Paul said he’s counting on small-dollar donations raised primarily online, the kind he’s tried to drum up during the debate that has resulted in at least the temporary suspension of the NSA’s authority to collect Americans’ calling records.

He’s attracted enthusiasm outside the usual Republican circles, particularly from college-aged voters with a distaste for military engagement and others who put civil liberties at the forefront of their concerns.

Republican pollster Frank Luntz, who isn’t aligned with any 2016 candidate, said what Paul lacks in traditional deep-pocketed donor enthusiasm, he could make up for in smaller contributors.

“He’s not going to have a traditional campaign because he’s not going to be a traditional candidate,” Luntz said. “That comes with advantages and disadvantages.”

Paul’s campaign said it raised more than $1 million online in his first 24 hours as a candidate, but wouldn’t say how much it has raised around the NSA issue. It will report on its finances next month.