Earlier this year, Gingrich faced conservative criticism when he rejected GOP Congressman Paul Ryan's plan to overhaul Medicare.
"I don't think right-wing social engineering is any more desirable than left-wing social engineering," Gingrich had said of the plan in May on NBC's Meet the Press. He later tried to downplay his remarks.
"Nobody doubts how smart he is--nobody has any doubts about the fact that he's got a lot of new ideas and that he wants to run things in a different way. But he's got some serious hurdles to jump," says John Geer, political science professor at Vanderbilt University. Geer adds that successful presidential candidates need to be extremely disciplined.
"Gingrich is not, though he's been of late. But I don't know how long that will last," he says.