I can’t remember who said it, but the gist was, that if Jeb! had Trump’s polling numbers for this long, he would have already been declared the winner.
Propaganda pieces like this are trying to replicate the somewhat successful strategy used by Romney against Thompson in a previous election: “He doesn’t really want it”, “He is thinking about quitting”, “No fire in the belly”, etc. The whole thing is designed to create hesitancy in the minds of the voters. Who wants to bet on a horse that will not finish the race, etc.?
On MSNBC this morning, Trump addresses these stories and his plan to stay the course.
"As Bloomberg’s John Heilemann said on “Morning Joe,” if Jeb Bush had Mr. Trump’s numbers everyone would declare the race over."