De Blasio Got Their Donations. Their Votes for President? Not So Much.

What about a President de Blasio? “I don’t know,” said Mr. Rusi, who owns a contracting company.

“Well, somehow I guess I’m going to have to support him,” he allowed. “He’s the mayor and everything.” (He expressed greater fondness for Mayor Pete Buttigieg of South Bend, Ind., and was seeking to organize a fund-raiser for him.)

At the home of Maninder Sethi in Old Westbury, Long Island, several dozen people gathered last fall to hear from the mayor and donate. Many of those present gave relatively small amounts, in the hundreds of dollars, and said they were brought together by common communal bonds, not by affinity for Mr. de Blasio.

“It was at my uncle’s residence,” said one attendee who runs an online cellphone store and requested anonymity to discuss his $4,500 contribution. “My uncle asked me to donate and I did it.”

Ravishankar Bhooplapur, the president of a medical school in Aruba, donated $500. He said he gives to “both parties” but had been a longtime supporter of the mayor, and would support his bid for president.

“Whether he appeals to the rest of the country, I don’t know,” he said of Mr. de Blasio. “As a New Yorker, I would love to have him.”

David Jiang, who described his business as importing and manufacturing, said he gave $5,000 during a Queens fund-raiser last year because “it just seemed like this was an opportunity to meet the mayor and give my point of view.”

“I support both sides,” he added.

For the moment, pricey fund-raisers are not Mr. de Blasio’s focus: He’s seeking donations as little as $1 to $3 from thousands of people, to meet the Democratic Party’s 65,000-donor threshold to qualify for the primary debate stage in June.