HOLLYWOOD, Fla. — Donald J. Trump’s newly installed campaign chief sought to assure members of the Republican National Committee on Thursday night that Mr. Trump recognized the need to reshape his persona and that his campaign would begin working with the political establishment that he has scorned to great effect.

Addressing about 100 committee members at the spring meeting here, many of them deeply skeptical about Mr. Trump’s candidacy, the campaign chief, Paul Manafort, bluntly suggested the candidate’s incendiary style amounted to an act.

“That’s what’s important for you to understand: That he gets it, and that the part he’s been playing is evolving,” Mr. Manafort said, suggesting that Mr. Trump was about to begin a more professional phase of his campaign.

“The negatives are going to come down, the image is going to change, but Clinton is still going to be crooked Hillary,” he added.