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 rival Ted Cruz seized on the leaked remarks, saying: “He’s telling us he’s lying to us.’
Five states go to the polls on Tuesday to pick their presidential candidates in the Republican and Democratic races.
Mr Trump’s 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.
He 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”.