Mr. Dimon said last year that he planned to remain at the bank’s helm for another five years. He has made clear that the bank’s two co-presidents, Daniel Pinto and Gordon Smith, could step in to replace him in a pinch if, as Mr. Dimon likes to say, he were to get hit by a bus.

But the question of who will replace Mr. Dimon in the long term is shaping up to be one of the most closely watched leadership contests on Wall Street.

A person familiar with Mr. Dimon’s thinking said he saw Ms. Lake and Ms. Piepszak — both 49 years old — as his likely successors in the long run. Other candidates include Douglas B. Petno, who runs JPMorgan’s commercial banking division, and Mary Callahan Erdoes, who is in charge of the asset-management group. Ultimately, that decision is not up to Mr. Dimon but to the bank’s board.

The executive changes came a week after Mr. Dimon and the chief executives of six other big banks were asked during a congressional hearing to raise their hands if it was likely that a woman or person of color would succeed them. None of the seven white men raised their hands.

“It has nothing to do with Marianne, I think Marianne is exceptional,” Mr. Dimon said when asked during a quarterly earnings conference call with analysts on Friday why he had not raised his hand. He said he and the other witnesses at the hearing had found the question confusing. “We don’t talk about succession publicly,” he added.