As Wall Street’s top bankers huddled in New York last month, preparing to convince Elon Musk’s SpaceX that they should be chosen to lead its upcoming IPO, one firm wasn’t letting its star advisor miss the bake-off.

Among the squad of JPMorgan Chase investment bankers flying 2,500 miles west to California to pitch SpaceX was the lender’s boss, billionaire CEO Jamie Dimon, people with knowledge of the trip told CNBC.

The morning after that pitch meeting, on Dec. 19, Dimon was already back in his customary early Friday perch: sitting in his bank’s New York lobby, taking meetings in full view of the thousands of employees streaming through the building’s turnstiles.

The whirlwind few days highlight the reality of Dimon’s singular impact on JPMorgan, the world’s largest bank by market capitalization.

Dimon marks his 20th anniversary as CEO this month and remains deeply involved across the sprawling businesses of JPMorgan, a giant across Wall Street and Main Street with $4.6 trillion in assets. Half a dozen executives across investment banking, asset management and consumer banking echoed that view.

Which makes the inevitable questions surrounding Dimon’s tenure loom large as he approaches 70 years of age. Dimon has for years maintained, somewhat tongue-in-cheek, that his retirement was perpetually 5 years away. In 2024, for the first time, he acknowledged that window was shrinking.

Will JPMorgan’s era of dominance be over when Dimon exits as CEO?

“Given his track record, anybody else would be a downgrade,” said Ben Mackovak, a bank board member and investor through his firm Strategic Value Bank Partners.

“I’m sure somebody else could grow into the role and surprise people,” Mackovak said. “But on day one, no one is going to be as qualified to run that bank as Jamie.”

In two decades, Dimon took a middle-of-the-pack American lender and, with his unique combination of judgment, paranoia, attention to detail and scope of vision, created a juggernaut of finance that the world hadn’t seen before.

During calm times, he invested aggressively for the future, and during periods of tumult, like 2008 and 2023, he avoided pitfalls that consumed other banks, allowing him to snap up three failed institutions.

Over the past 20 years, the bank’s annual net income soared more than 500% to $58.5 billion in 2024. The firm reports full-year 2025 results on Tuesday.

Now, at a market cap of roughly $900 billion, JPMorgan is worth nearly as much as the next three largest U.S. banks combined: Bank of America, Citigroup and Wells Fargo.

Besides running JPMorgan, Dimon has taken on an outsized role in global finance as a top voice explaining market gyrations or emerging risks and influencing regulators amid policy shifts. It was Dimon’s recession warning on a Fox News segment in April that helped convince President Donald Trump to pivot on his trade policy, igniting a historic relief rally.

“It’s just the aura he has, the credibility that he’s built up in the markets,” said Fitch Ratings analyst Chris Wolfe. “The minute you step out of that role, it’s not like you can just hand that over, your successor doesn’t automatically inherit that. I think that’s the real challenge.”

The question of who could take over for Dimon — who was already a cancer survivor when he nearly died in 2020 from a ruptured aorta — has been openly discussed among investors for more than a decade.

To investors, his most likely successor is currently Marianne Lake, head of the firm’s giant consumer bank and former CFO of the company, followed by Doug Petno and Troy Rohrbaugh, the co-heads of the firm’s commercial and investment bank.

Other contenders include asset and wealth management head Mary Erdoes and CFO Jeremy Barnum.

“If investors were to do a straw poll today, they’d probably pick Marianne,” said Truist bank analyst Brian Foran.

“The running joke is that she’s a human supercomputer when it comes to banking,” Foran said. “Really, the only question mark people have about her is, she’s so analytical, can she do the kind of ‘rah-rah’ stuff to inspire the sales force?”

Wells Fargo banking analyst Mike Mayo hypothesized that JPMorgan stock could immediately drop 5% if Dimon were to suddenly exit, regardless of the named replacement. (The bank has said Dimon would serve as chairman even after relinquishing the CEO role.)

It’s a somewhat common occurrence on Wall Street for companies with iconic CEOs: The stock premium shrinks, at least for a period, when their longtime leaders announce their departures. For instance, Berkshire Hathaway shares trailed the S&P 500 last year after Warren Buffett said he was stepping down as CEO.

In recent months, Dimon oversaw the completion of the bank’s new $3 billion headquarters in midtown Manhattan and announced a $1.5 trillion initiative to bolster industries crucial to U.S. interests.

And, perhaps most crucially, he continues to instill his values into the firm’s management team.

Last year, at a conference for JPMorgan’s top 400 executives, Dimon rattled off a list of once-great companies that died though mismanagement. Finance is especially prone to this threat, because of the temptation to manipulate numbers for short-term gain, he said.

“Travelers blew up. Citi blew up, twice. Bear Stearns failed, Lehman failed, I’m here because Bank One screwed up a bunch of businesses,” Dimon said, referring to a predecessor firm to JPMorgan.

“If you look at these things, it’s complacency, it’s bureaucracy, it’s arrogance. A lot of it is dishonest numbers. Failure to set standards,” Dimon said. “These are the cancers that kill companies.”

Nobody knows when Dimon’s last day as CEO will come, except to know that it is approaching. After adjusting his standard 5-year retirement answer to hint at a sooner departure, Dimon hasn’t advanced that clock any further.

“As great as he is, he can’t do this forever,” said Barclays banking analyst Jason Goldberg. “Every day that passes, you’re a day closer to the end.”

— CNBC’s Gabriel Cortes contributed to this report.