When New York wanted to lure Amazon to western Queens with more than $2 billion of public money in 2018, an ascendant left wing rallied to defeat it. Progressive politicians, headlined by Representative Alexandria Ocasio-Cortez, condemned the move as a corporate giveaway that would accelerate gentrification.

Seven years later, a much bigger project is on the table. This time it’s not about granting hefty public subsidies to one of the biggest companies in the world. Instead, New York City is proposing a huge rezoning in the area that would allow private developers to construct almost 15,000 apartments across 54 blocks currently filled with warehouses and parking lots. A vote in the City Council is expected at the end of the month.

The response from Zohran Mamdani, New York’s progressive standard-bearer and the Democratic nominee for mayor, has been unmistakably warm.

“I’m always excited about the prospect of building additional housing,” Mr. Mamdani, who also represents the area in the state assembly, said during a recent interview with Errol Louis on NY1.

The contrast in tone, from both Mr. Mamdani and the left more broadly, reflects fundamental differences between the plans of 2018 and today.

The Amazon effort, with $1.7 billion in incentives from the state and hundreds of millions more from the city, was hatched by company executives and city and state officials. The new plan, in contrast, has followed two years of open negotiations among civic leaders, city officials and residents, and puts a priority on benefits for New Yorkers like affordable housing and park space.

But the shift also underscores how the left has increasingly changed its posture toward encouraging private development as a means to solve the city’s housing crisis. It also highlights how Mr. Mamdani, a democratic socialist, has a more nuanced position on addressing New York City’s housing crisis that is often overshadowed by his uncomplicated pledge to freeze rents on rent-stabilized homes.

In addition to the Long Island City plan, Mr. Mamdani has spoken favorably about Mayor Eric Adams’s push to unleash development across the city, otherwise known as “City of Yes.” In an interview with The New York Times earlier this year, he said he now accepts that “there is a very important role” for the private sector to play in building homes, acknowledging that it was a position he did not previously embrace. He has spoken about finding ways to reduce insurance premiums for landlords and red tape for developers.

“I think he is generally a pro-development progressive,” said Alicia Glen, a deputy under former Mayor Bill de Blasio, who was involved in the negotiations with Amazon.

Mr. Mamdani’s top opponent in the mayor’s race, former Gov. Andrew M. Cuomo, was one of the architects of the Amazon deal and has made private development a centerpiece of his housing agenda.

Mr. Mamdani’s campaign declined to answer questions about his position on the plan, pointing instead to comments he made in the NY1 interview on Sept. 25. A spokesman for his assembly office did not respond to questions about the rezoning, referring them to his campaign office.

“We are in an affordability crisis,” Mr. Mamdani said in the NY1 interview. “We are in dire need of additional housing. And that housing has to be built all across New York City. I’m excited to be the mayor that finally delivers that.”

The housing crisis is a top issue in the mayor’s race. The city is dealing with the worst housing shortage it has faced in nearly 60 years, and rents remain high, threatening the city’s economy and making it difficult for average people to afford to live here.

City officials hope that encouraging more development in Long Island City, which has good access to public transportation and offers short commutes to the corporate offices and tourist attractions of Midtown Manhattan, will be a big part of the solution.

Already, parts of Long Island City are booming. After a 2001 rezoning, several towering luxury apartment buildings sprouted in the area, yielding almost 28,000 new housing units between 2010 and 2024 according to Planning Department data, and making the neighborhood one of the fastest-growing places in the country.

The new plan would target blocks that were not part of the 2001 rezoning but are in the same general area. They have long been an alluring site for development — there have been at least five attempts to build on portions of the site since 2015, including in the Amazon deal — but nothing has yet come to fruition.

City officials estimate that a new rezoning, as currently formulated, would make way for 14,700 additional homes, including 4,300 restricted to people of lower incomes that would most likely rent at below-market rates. The plan would also add waterfront park space and create commercial space that could yield some 14,400 jobs, according to city estimates.

It must, however, be approved by the City Council, which would all but require a go-ahead from Julie Won, the council member who represents the area. The Council traditionally respects the sway of the local representative, a practice known as member deference.

In an interview, Ms. Won recalled being part of the opposition to Amazon. “It didn’t reflect anything that our community actually needed,” she said.

She recalled celebrating that plan’s demise by smashing a piñata that displayed a picture of the head of the company’s founder, Jeff Bezos.

Now, she said, she wants rezoning to move forward, though she has not yet given the city’s plan her endorsement. She said her support hinges on a commitment to more affordable housing than the city is proposing, a connection between nearby parks situated along the waterfront and improvements to local schools, public housing and sewers.

She said that Mr. Mamdani has told her that he agrees with her “red lines.” In the NY1 interview, he said he is taking Ms. Won’s concerns seriously, and that rezoning should be coupled with investments in infrastructure and an increase in connections along the waterfront between neighborhoods that have historically been split apart and segregated.

“These are things I would examine very closely,” he said.

Ms. Won said if the city doesn’t change the plan in the coming weeks to address her priorities, she would reject it and work with Mr. Mamdani, should he win the election, to come up with something better. “We’re together on this,” she said.

Ms. Glen, now the founder and managing principal at MSquared, a development firm, said it would be “naïve” to push the rezoning into the next administration, which might want to spend money on other priorities.

“It’s a tough needle to thread,” she said.

Ms. Won’s skepticism of the city’s effort — echoed by activists and other constituents during Council hearings — illustrates the difficult position Mr. Mamdani is in. Many in his political base are wary of the involvement of private developers in housing solutions and prefer public investment, a dynamic that does not fully align with the city’s plan in Long Island City.

“When we are facing this level of housing crisis, I support only deeply affordable housing,” said Mary Jobaida, a democratic socialist who has lived in Long Island City for 20 years and is running for Mr. Mamdani’s assembly seat. “No mixed income. We need to solve the immediate problem.”

Ms. Jobaida, who immigrated from Bangladesh, opposes the city’s plan, as she opposed the Amazon development. “Our fight continues,” she said.