That's what millions of people are asking after reading a NYT article contrasting the "bombastic" Donald Trump to Jeb Bush who is described as "the wonky son of a president." Bush has repeatedly said that he can generate 4.0 percent GDP growth during a Bush presidency.
The baseline projection for the years 2017 though 2025 from the Congressional Budget Office is 2.1 percent. Raising this to 3.0 percent would be a remarkable accomplishment. There is no remotely plausible story that would raise growth to 4.0 percent. It would be sort of like predicting a baseball team going undefeated through 162 game season. It would be difficult to take seriously a team manager who confidently made such predictions. The same should apply to a presidential candidate boasting of 4.0 percent GDP growth.