At the Cantor event, Mr. Obama arrived on stage nearly a minute after the brokerage firm’s chief executive, Howard Lutnick, introduced him. “I’ve got to work on my entrance timing,” Mr. Lutnick joked as he waited, and waited, by the microphone.

After his prepared remarks and a few longer questions, Mr. Obama participated in what Mr. Lutnick called a “lightning round.” But Mr. Obama ended up fielding only one inquiry — about technology and government health care costs — and answered it soberly and at length, running out the clock. Mr. Obama then beseeched the audience of health care business professionals to keep the sick and scared at the core of what they did.

“If you’re going to make money this way, you better think about it,” he said.

Cantor Fitzgerald, which lost more than 600 employees on Sept. 11, 2001, in the attack on the World Trade Center, is not a top-tier player in investment banking. Leaner and less well-known than Wall Street blue-bloods like Goldman Sachs and JPMorgan Chase, it brokers trades and gives strategic advice to small and midsize corporations. Health care is one of its specialties.

Still, its crowd on Monday was full of marquee industry names, with representatives from hedge funds like Citadel and Balyasny, investment firms like Bain and Ares, and biotech companies like Amgen. Most of the attendees were Cantor clients.

Not everyone, however, was laser-focused on the guest of honor. Before the main event, some attendees made a bet on how late the speech would start — one guessed 20 minutes, another guessed 30. In one of the venue’s spillover rooms, where roughly 200 people watched the former president on a video monitor, a man in the back row dozed off while others texted or nibbled on pastrami baguettes.

Last week, Mr. Obama called attempts to undo the Affordable Care Act “aggravating” at a Gates Foundation event and on Monday he called them a cynical political exercise. Hours later, the opposition of a key senator appeared to leave the latest repeal bill without the necessary support to pass.

He acknowledged that the current system has problems, including that some states had not expanded Medicaid to the extent allowed by the A.C.A., and that some insurers were not providing coverage to parts of rural states. The solution to the lack of coverage, he said, was a public fallback plan.