For one thing, one of the payments to Mr. Edwards’s mistress took place as he was ending his candidacy, which further muddied how to interpret his motivation. By contrast, the payments to Ms. McDougal and Ms. Daniels came just ahead of the election.
For another, prosecutors in the Edwards case had little corroboration from other key figures in the transactions to explain their motivation. One of the supporters of Mr. Edwards who provided the funds, Fred Baron, had died, and the other, Bunny Mellon, was a 101-year-old recluse prosecutors did not seek to drag into the courtroom as a witness.
By contrast, a key figure in both of the Trump transactions, Mr. Cohen, is available as a witness and has already admitted his principal purpose in helping pay off the women was to “suppress the stories and thereby prevent them from influencing the election,” as the sentencing memo said.
Still, prosecutors themselves have accused Mr. Cohen of “a pattern of deception that permeated his professional life,” and Mr. Trump’s defense lawyers would certainly attack his credibility. Mr. Trump foreshadowed that strategy on Monday. “Cohen just trying to get his sentence reduced,” he wrote on Twitter. “WITCH HUNT!”
Citing the Edwards mistrial, Mr. Hasen said that federal prosecutors would be reluctant to go forward with a similar case against Mr. Trump unless they had credible corroborating evidence, especially in documentary form, to back up their accusations about what Mr. Trump was thinking about his campaign, not his personal life, when he instructed Mr. Cohen to arrange the payments.
“We don’t know everything the prosecutors have, and it really depends on that,” he said. “We don’t know if this is the sum total.”
Any other evidence that prosecutors might have to buttress Mr. Cohen’s potential testimony remains unclear. But Mr. Cohen has released a recording of a phone call in which he and Mr. Trump discussed the payment to Ms. McDougal, and the sentencing memorandum refers to other recordings of meetings and conversations that Mr. Cohen secretly made related to the payments, without providing details.