Joe Biden’s disastrous results in Iowa and New Hampshire have spooked Democratic donors who are preparing to jump ship and throw their money behind someone else — even as his campaign vowed Wednesday that the best is yet to come.

New York heavyweight donors raising money for Biden are alarmed by the former vice president’s fifth-place finish in the New Hampshire primary and are privately wondering whether he can make it to Super Tuesday on March 3.

“There’s a great deal of concern,” said a donor who is bundling contributions for a Biden fundraiser in New York Thursday.

“It wasn’t expected that he would perform great in Iowa or New Hampshire. But we did not anticipate that he would fare this poorly. It was a significant decline,” said the bundler, who requested anonymity.

Still, the Biden campaign was trying to project an image of strength Wednesday.

His camp released a new ad on social media that optimistically declared, “This is only getting started” — after he bolted from the Granite State before the polls had closed.

Biden even gave a speech to the supporters he’d abandoned in New Hampshire, from South Carolina on Tuesday night as the dreadful results rolled in and staff began panicking.

“This is horrendous. We’re all scared,” a Biden adviser told Politico. “I think we’re going to make it to South Carolina. I know we’re supposed to say we’re going to and we’re going to win. But I just don’t know.”

Gov. Andrew Cuomo is believed to have helped Biden’s struggling campaign raise money, but the feeling among Democrats is turning grim.

“The word that is going around most of my colleagues in politics is that it’s sad,” veteran Democratic consultant George Arzt said. “No one wants someone to end their political career on a down note. He is a very ­decent man.”

There’s also the Mike Bloomberg factor. The billionaire former three-term mayor has peeled off support from Biden in New York’s corporate class, sources said.

“Even before this setback, Biden has struggled to raise money this election cycle. It’s hard to see how he raises the money to propel him forward,” one source told The Post. “I know a lot of people who are with Bloomberg.”

Kathryn Wylde, head of the NYC Partnership, said a lot of the regular New York Democratic donors are still with Biden, but now “some are holding out” for Bloomberg.

Another source said Bloomberg has won over some corporate honchos who’ve regularly contributed to Cuomo’s campaigns.

Cuomo on Wednesday conceded that while the former veep had “not done well,” he was not ready to give up on him yet.