Mayor Bill de Blasio was only able to convince 17,500 donors to back his doomed presidential campaign – a mere 13 percent of the 130,000 unique contributions he needed to qualify for the fall Democratic primary debates.

“A lot of factors went into the decision,” to drop out of the race, campaign spokesman Jon Paul Lupo told The Post. “Debate qualifications was one of them.”

De Blasio raised $1.1 million from 6,700 donors during the first six weeks of his campaign. That momentum slowed considerably during the next 12 weeks when he brought in just $333,000 from another 10,800 supporters.

The long-shot candidate blew through nearly all the money he raised during his short-lived campaign. He has just $43,000 left in his 2020 account. Lupo says de Blasio has no plans for the money and there may be more bills that come in.

Many of de Blasio’s top donors have real estate interests in the city. John Byrne, managing director of National Land Tenure that insures major Big Apple properties including Hudson Yards and Stuyvesant Town, gave the maximum $2,800.

Samuel Agnoli and Jonathan Blank, two senior staffers with Property Markets Group, each donated $2,800 in July. Their firm is building 111 W. 57th Street, one of the “supertall” towers that de Blasio defended in a September interview on WNYC.

“I don’t believe they have destroyed, you know, life in New York City in any way,” de Blasio said in response to a caller named Stacey from the South Street Seaport area who asked the mayor if he could “prevent the proliferation of these supertall buildings around the city.

“I don’t love them,” de Blasio said while adding that he wasn’t going to consider banning them.

“There’s a lot better things to worry about than this handful of supertall buildings,” he said.