JPMorgan Chase (JPM) Chief Executive Officer Jamie Dimon won majority support from investors to keep his chairman title in preliminary voting ahead of today's shareholder meeting, according to two people with knowledge of the tallies.

Still, Dimon was on track to get less support for retaining the dual roles than at last year's meeting, when 40 percent of shareholders favored naming an independent chairman, the people said, requesting anonymity because the vote count isn't public. The outcome could change as final ballots are cast today. Joe Evangelisti, a spokesman for the New York-based lender, declined to comment on the voting.

Calls for Dimon, 57, to cede the chairmanship have mounted since last May, when JPMorgan disclosed lapses in risk controls at its chief investment office that led to more than $6.2 billion in losses on derivatives. Bruno Iksil, the trader who made the bets, was nicknamed the London Whale because his position was so big.

The New York Times reported Dimon's lead in preliminary voting earlier today.

Dimon received backing from investors including Home Depot Inc. founder Ken Langone, who called the banker the "finest" CEO in the U.S., and billionaire Warren Buffett, the Berkshire Hathaway Inc. chairman and CEO who has described Dimon's annual letter to shareholders as a must-read.

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