"Donald J. Trump has shaken up his presidential campaign for the second time in two months, hiring a top executive from the conservative website Breitbart News and promoting a senior adviser in an effort to right his faltering campaign. 

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. 

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. 

The 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. 

“It’s an expansion at a busy time in the final stretch of the campaign,” she said, adding that Mr. Manafort and his deputy, Rick Gates, would remain in their roles. 

“We met as the ‘core four’ today,” Ms. Conway added, referring to herself, Mr. Bannon, Mr. Manafort and Mr. Gates. 

People briefed on the move said that it reflected Mr. Trump’s realization that his campaign was at a crisis point. But it indicates that the candidate — who has chafed at making the types of changes his current aides have asked for, even though he had acknowledged they would need to occur — has decided to embrace his aggressive style for the duration of the race. 

Both Ms. Conway and Mr. Bannon, whose news organization has been very favorable to Mr. Trump since he entered the primaries, are close with Robert and Rebekah Mercer, the father-and-daughter conservative donors who have become allies of the candidate and are funding a “super PAC” that is working against Hillary Clinton."