The 2015 period coincides with Mr. de Blasio’s work in Albany with the Real Estate Board of New York, an industry group, to get state lawmakers to renew — with some changes — a city subsidy for developers known as 421-a.

Over the same months, the Campaign for One New York spent about $700,000 on political consultants, national travel and research as the mayor worked to bolster his progressive agenda — and profile.

[. . .]

The mayor’s advisers said people are giving to the group because they support Mr. de Blasio’s positions on issues like affordable housing and prekindergarten. They emphasized the group is limited to issues advocacy and can’t directly support a re-election bid by Mr. de Blasio.

[. . .]

Since its inception on Dec. 12, 2013, the operation known as Campaign for One New York has accepted $3.87 million from dozens of real estate developers, unions and others who do business with City Hall. The setup allows the mayor to raise money outside the regulations of the city Campaign Finance Board.

The contributors to his group include individuals and firms seeking approvals for their projects, and they often donate through limited liability companies that obscure their identities.

In some cases, donors gave money right before or after getting a city-granted benefit, according to a POLITICO New York review of $1.71 million in individual contributions that poured in during the first six months of 2015.

[. . .]

In March, District Council 37, the city’s largest municipal union, donated $20,000 to the campaign. Around that time, the union’s leadership was successfully negotiating raises for its lowest-paid members with the city Office of Labor Relations.

“DC 37’s support for the Campaign for One New York’s efforts to draw attention and find solutions to the city’s affordable housing crisis is based solely on merit,” DC 37 executive director Henry Garrido said in a statement to POLITICO New York.

For their place in the mayor’s orbit, these consultants have been well compensated: In the first year and a half of his term, their firms have collected nearly $2.3 million in payments. Most of the money has come from a nonprofit organization, the Campaign for One New York, that was created by political professionals from his mayoral campaign as a vehicle to push his initiatives, and whose donors have included real estate developers and unions.

Through the middle of this year, 77 percent of the group’s spending went to several consulting firms that also worked for Mr. de Blasio’s 2013 campaign.

The mayor’s reliance on private consultants seems to run contrary to the image he has cultivated. As mayor, he has criticized the role that the “consultant class” played in politics; in his previous elective office, as the city’s public advocate, he assailed the influence of political donors hiding behind “political committees that masquerade as tax-exempt nonprofits.”

Yet a review by The New York Times of hundreds of pages of the mayor’s daily schedules, as well as email correspondence and other records, shows the central role that private consultants have played in his administration. The correspondence highlights how some consultants have almost unfiltered access to City Hall, with the dialogue conveying a casual atmosphere.

[. . .]

As public advocate, Mr. de Blasio condemned the growing role of “shadowy” nonprofit groups, calling them “a threat to our democracy.”

But as mayor, Mr. de Blasio has embraced the Campaign for One New York, the nonprofit group that has provided steady income for several consulting firms he relies on.

The campaign was started in December 2013, just after Mr. de Blasio was elected. Bill Hyers, who had been his campaign manager, serves as its chairman. The group has supported the mayor’s agenda, advocating, for instance, the expansion of prekindergarten that was the signature issue of the de Blasio campaign. It has also retained a lineup of consultants who are close to the mayor.

Ms. Hinton said the nonprofit’s involvement did not contradict the mayor’s previous stances because of its mission, and because it disclosed its donors and expenses. She said the group “does not engage in politics” but “exists solely to advance the administration’s agenda,” and she called its creation “not unprecedented or unique or anything.”

Mr. de Blasio has been active in helping to raise money for the Campaign for One New York, which can accept unlimited donations. By doing so, he has bypassed the city’s campaign finance laws that would ban or strictly limit certain contributions, including those from corporations and limited liability companies and from people who have business dealings with the city. The nonprofit has received a number of six-figure donations, including $350,000 from the American Federation of Teachers and a pair of $250,000 contributions from 1199 S.E.I.U. United Healthcare Workers East.

“Transparency and responsiveness in government decisions and policies engenders trust in our democratic process,” he said in 2013.

[. . .]

So how would de Blasio rate his own administration using his own criteria?

For months, the mayor’s allies objected to accusations that Mr. de Blasio wanted to play kingmaker, saying that he simply wanted to hear more detail about the policy plans of presidential contenders, particularly at an early stage of the campaign.

More recently, however, the mayor’s inner circle had grown frustrated with his delay in endorsing, saying that the uncertainty had become a distraction.