Donald Trump has promised to change his image, in a closed-door meeting with Republican party leaders.
The businessman, who leads the party’s race to be presidential nominee, delivered his message via aides, the Associated Press news agency reports.
His success in primary elections so far has set off alarm bells among those in the party anxious that his tone and policies will turn off voters.
Five states go to the polls on Tuesday to pick their presidential candidates.
Mr Trump has a clear lead in the number of delegates but may fall short of the 1,237 threshold required to win the nomination without a contested convention – where the nominee is chosen through negotiations among party figures.
In a recording of Thursday’s meeting obtained by Associated Press, his senior aides told Republican leaders that he has been “projecting an image” so far and “the part that he’s been playing is now evolving”.
In it, his newly hired senior aide, Paul Manafort, told the Republican National Committee members that Mr Trump has a campaigning personality and a private one.
“When he’s out on the stage, when he’s talking about the kinds of things he’s talking about on the stump, he’s projecting an image that’s for that purpose,” he said.
He knows he needs to moderate his personality, Mr Manafort told the meeting. “The negatives [unfavourable ratings in polls] will come down. The image is going to change.”
His standing among female voters is particularly low, after a series of controversial remarks about women, abortion and rival Ted Cruz’s wife.
Analysts say Mr Trump’s decisive win in the New York primary this week seemed to signal a new, softer side in his victory speech.
And he told a rally in Pennsylvania on Thursday: “At some point, I’m going to be so presidential that you people will be so bored.”
On one of the key social issues currently engulfing the party, transgender rights, he took a stance out of step with his key rival Mr Cruz on Thursday, when he said transgender people should be allowed to use a toilet assigned to a gender of their choosing.
Mr Cruz criticised this as politically correct but former candidate Ben Carson praised Mr Trump for “trying to moderate”.
Mr Trump has accused the RNC of conspiring against him and of rigging the way delegates are awarded in a way that is unfavourable to him.