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In testimony before Congress this week, Michael Cohen cast himself as a central figure in schemes that could threaten the presidency of Donald J. Trump.

But Mr. Cohen said he didn’t work alone, unexpectedly mentioning by name the involvement of another member of Mr. Trump’s inner circle, Allen Weisselberg, more than 20 times. The revelations are set to intensify the scrutiny on Mr. Weisselberg, Mr. Trump’s unassuming 71-year-old chief financial officer, who already is a focus for federal prosecutors in New York.

On Wednesday, Mr. Cohen specifically identified Mr. Weisselberg as helping mastermind a strategy to mask reimbursements to Mr. Cohen for his payment to Stormy Daniels, the pornographic film actress who said she had an affair with Mr. Trump.

Representative Elijah E. Cummings of Maryland, chairman of the House Committee on Oversight and Reform, said after Wednesday’s hearing that he “probably will” want to call additional witnesses, including Mr. Weisselberg, to gather additional evidence about the hush-money payment.