Trump, who will moderate a GOP candidate debate on Dec. 27, said Romney struggles to stay in front, saying "I don't know what it is." In an interview on NBC's "Today" show, Trump defended Romney against assertions by critics that he has flip-flopped on issues like immigration, abortion and health care. Trump said "we all change our minds on things."
Only former House Speaker Newt Gingrich has accepted an invitation to the December debate in Des Moines.
In the interview, Trump also labeled Rep. Ron Paul and former ambassador Jon Huntsman as "joke candidates," and defended his plan to moderate the face-off, which will take place as the Iowa caucuses draw near.
Trump said that "a lot of Republicans, top Republicans, asked me to do the debate." And he also said that if he isn't satisfied the GOP is putting up a viable candidate against President Barack Obama, "I would certainly think about running as an independent."