Expressing confidence that American voters do not care if he lacks specifics, Donald J. Trump says he has yet to fully exploit his personal advantages over his Republican presidential rivals — chiefly his enormous wealth and celebrity — and that both will matter more to his political fate than debate performances like his shaky one this week.

Mr. Trump said in an interview that he was prepared to spend $100 million or more to become the Republican nominee and that most of it would go to galvanizing voter support in states with early nominating contests. While he boasted last month that he would spend $1 billion if need be, he said that a realistic amount would be far less and that he would count on the national Republican Party for financial help if he became the nominee.