Easy. Because the media is doing to him what it did to Romney and McCain in the last two election cycles. During the primaries, no matter how outraged journalists were at what Trump said, the presentation was always the same: Trump the unstoppable. Even when they asked if his latest escapade would finally derail him, the conversation was inevitably wrapped up in a narrative of Trump, who the others simply cannot stop.
Fast forward to now. For the last three weeks, the coverage has changed. Oh, they're still covering Trump. But now it's Trump the defeated, Trump the loser, Trump falling behind, Trump unable to keep up, Trump losing his own party. The 'feel' of the stories is different. Now it's almost the inevitability of Trump's loss to Hillary. Almost as if to say, "Can't we just concede the inevitable?"
Meanwhile Hillary has, as far as I know, done nothing wrong. If there are still scandals or hearings or news suggesting she's in trouble, I've not heard of it. Perhaps it's been mentioned in passing, or tucked in behind the Want Ads and the Grocery Ads. But on the whole, it's been a triumph after triumph for Hillary. A far cry from those hazy days last year when it looked like Joe Biden might run, and you had the press surprisingly jumping on one Hillary scandal after another.
The same thing happened with McCain, and more flagrantly, with Romney. And, to a point, it happened with Bernie Sanders. It's not hard to see the role that the media played in ensuring that no matter how many victories Bernie had, he was still the loser. In 2012, during the primaries, if Romney did anything wrong, we never heard it. Even if he was at the head of the polls, we only heard about the next Republican in line who was put under the microscope. It wasn't until Romney clinched the nomination that we suddenly heard story after story, unpacking every minute detail of Romney, his past, his Mormonism, his wealth, his gaffes.
Don't think, for a minute, propaganda doesn't work. It always has to a point. With mass media, a new level of effectiveness was achieved. We have the two candidates the national media wanted us to have, when the dust settled and certain things - like Biden's refusal to run - were factored in. Now guess which one the media wants to win. And watch and see the different approach the media will take. Assuming Trump really wants to win and isn't some plant or just doing it as a publicity stunt, I'm afraid that he's in for the biggest uphill battle of his life.