IIRC, the Romney campaign said after the fact in 2012 that Obama's ad buys really did them in in a couple of states - specifically early-morning ads targeted at the elderly. It appears Trump didn't learn this lesson.
Trump is not Romney. Just about everyone knew who he was before the primaries and after.
As such, Trump's pretty well defined already. Romney got slammed with the Bain Capital stuff and was defined as the moneybags candidate this time last cycle, (which is why I thought he was a TERRIBLE candidate).
It's not as easy defining Trump. People already associated him with "You're Fired!" prior to the election and they know he wants to build a wall and get Mexico to pay for it.
