And much of Mr. Mamdani’s agenda relies in large measure on increasing revenue through taxes on businesses and the wealthy — part of an overarching vision to rethink how the city funds expanded social programs. Along with raising income taxes, he has pledged to shift the property tax burden “from the outer boroughs to more expensive homes in richer and whiter neighborhoods,” according to his campaign website.

Already, Mr. Mamdani’s plans, in line with his democratic socialist political affiliation, have prompted intense backlash from business leaders who say he poses a danger to New York’s economy. In private meetings, power brokers are discussing how to mount a strong challenge to Mr. Mamdani in the November general election.

But the obstacles are not just political. To accomplish most of what he has promised, he will have to combat powerful headwinds from Albany and Washington that threaten to stymie his ambitious agenda.

Raising Revenue

Mr. Mamdani faces significant roadblocks in his effort to raise taxes. The nature of Albany’s budget process gives immense leverage to Gov. Kathy Hochul, who is up for re-election next year and has promised no increases in state income taxes.

Mr. Mamdani is proposing a new income tax of 2 percent on residents making more than a $1 million a year, which he estimates would bring in about $4 billion year. He also wants the state to sign off on an increase of the top corporate tax rate to 11.5 percent, up from 7.25 percent now. This would generate an extra $5 billion a year, according to his campaign.