Bill de Blasio delivered on Friday his most detailed blueprint yet for how he would reimagine New York as a more equitable and populist metropolis, even as he works diligently behind the scenes to send a subtler message to the city’s corporate titans: He is not their enemy.

In a speech before a prominent civic group, Mr. de Blasio, the Democratic nominee for mayor, denounced giveaways to the real estate industry, pledged to re-energize labor unions and declared that the city’s “affordability crisis” was as urgent and serious a problem as the turmoil faced after the Sept. 11 terrorist attacks.

“We cannot expect prosperity to trickle down from the top,” he said during the speech in Midtown Manhattan, adding, “We cannot resign ourselves to the mind-set that says rising inequality is a necessary byproduct of urban success.”

He was met with a standing ovation from an overflow crowd of wealthy business leaders — the same group that a year ago had responded to a similar speech by Mr. de Blasio with chilly disregard.