David Adelman is officially a Sixers limited partner. Their arena plans rise and fall with him.

There’s a mixture of nostalgia and aspiration in David Adelman’s vision of a downtown arena for the 76ers. There’s a sweet spot there for someone of Adelman’s background and generation, and he’s determined to find it for the sake of shaping what he insists will be a better Philadelphia.

“That’s all we’re trying to do,” he said in an interview last month.

A native of Penn Valley, a developer who built his business by transforming some of West Philadelphia into all of University City, Adelman is 50, a Gen-Xer who bridges the Philly that can’t exist anymore and the Philly that might yet. Who references, with fondness, the days when Gimbels and Wanamaker’s and Strawbridge & Clothier made Market East the commercial center of the city. Who now wants to marry that yearning for the past with the modern necessities that would accompany a pleasure palace at 10th and Market: improved public transportation, partnerships with parking-lot companies and restaurants in Chinatown, the trust from civic leaders and community members that the Sixers weren’t in this strictly for themselves.

Those are tall orders, even for a project that, if it gets a green light, is targeted for completion nine years from now. But now that Adelman has purchased much of Michael Rubin’s share of the Sixers, now that he’s a limited partner in the franchise and not just a collaborator with it, now that one of the worst-kept secrets in Philadelphia sports is out of the bag, he becomes more than just a running buddy for managing partners Josh Harris and David Blitzer. He is the local face of this campaign, and the Sixers have to hope that he can quell the cynicism, the skepticism, and the realities that stand in the way.

» READ MORE: David Adelman purchases share of Michael Rubin’s HBSE stake to become Sixers limited partner: ‘I’m excited to be involved in a small way’

Yes, they have to hope that Adelman has those connections and credibility, because no one else does. Harris Blitzer Sports & Entertainment is a business behemoth, one that already tried to secure an arena project in Penns Landing, one that doesn’t like to lose. It would be naive to think that, if Harris Blitzer failed in this second bid, it wouldn’t consider relocating the Sixers, despite Adelman’s on-the-record assurances that the franchise will remain in Philadelphia, no matter where the Sixers have to play their home games once their lease with the Wells Fargo Center expires in 2031.

“Let me be really clear about this,” Adelman said. “When Josh and David asked me to get involved in this, which was after the Penns Landing thing, I said, one, we have to be a three-way partnership, or a four-way when you count HBSE. Two, we won’t threaten to move the team. Three, we have to do something really good for the city. And four, not take any [public] money. They were fully aligned.”

That’s not the key question anymore. The key question is, will they remain aligned? And Adelman will have to do some persuading — of the next mayor, of City Council, of the residents of Chinatown and the neighborhoods surrounding the proposed site, of Sixers fans throughout the region — that they will, that this venture will fulfill every promise and meet every expectation.

David Gould, the Sixers’ chief diversity and impact officer, said that he and Adelman meet with Chinatown community members three times each week, asking them how, say, a major event at the Convention Center affects their businesses. Such research and relationship-forging expeditions are the bare minimum of preliminary work for the Sixers, because they have begun to make promises and raise expectations, because they already have started to stretch some of their initial parameters for the project.

“When I look at Chinatown, I see it on the seesaw,” Adelman said. “It’s either going to be a melting ice cube, or it’s going to go to the next level. This is where we can build that solid foundation. We want everyone to play here. This is going to be the community’s arena, from Big 5 basketball to community events, obviously concerts, and the Sixers. I think we’d love to see a WNBA team here. I don’t know how soon that’s going to happen, but the more, the merrier.

“Of all the real estate deals I’ve ever done, this will be the biggest individual check I’ve put into a deal for the lowest return,” he added. “That’s the truth. I’m sure no one’s crying for me, but that is the truth. This is a socio-economic return for me, not a financial return.”

» READ MORE: Point man for Sixers’ arena plan: ‘The city’s not going to fix itself’

It’s also an easy thing for a billionaire developer to say now, before he starts to make demands, before demands start to be made of him. But then, that’s the line that David Adelman has chosen to walk here. He now speaks for the Sixers, and he wants to speak for Philadelphians. The proof of his words and his commitment, though, will be in what he and his partners do, and how they go about doing it.