Stephen Bannon, the executive chairman of Breitbart News LLC, will become the Republican campaign's chief executive, and Kellyanne Conway, a senior adviser and pollster for Mr. Trump and his running mate, Gov. Mike Pence of Indiana, will become the campaign manager, NYT wrote.

Paul Manafort, the campaign chairman, will retain his title. But the staffing change, hammered out on Sunday and set to be formally announced Wednesday morning, was seen by some as a demotion for Mr. Manafort.

Read alsoNYT: Secret ledger in Ukraine lists cash for Donald Trump's campaign chiefThe news, first reported by The Wall Street Journal, was confirmed early Wednesday by Ms. Conway in a brief interview, but she rejected the idea that the changes amounted to a shake-up and said that Mr. Manafort was not being diminished.

Mr. Manafort had come under increasing scrutiny over his ties to Ukraine for elections he worked on as an international consultant, including handwritten ledgers showing he was designated to receive $12.7 million in undisclosed cash payments from a pro-Russian political party from 2007 to 2012. Yet it remains to be seen whether a new chain of command can ultimately fix the problem: the candidate's lack of discipline and desire to punch back at nearly any critic.