Static analysis fail. When the situation changes the players' tactics change in response. June 2015, Trump is seen as a joke who will hurt the GOP brand just by associating himself with it. Liberals play into his self promotion on the assumption that he will either implode or be easy to beat in the general. Trump, a master tactician, uses this to increase his standing and garner millions of dollars worth of free air time from his enemies. It's the campaign equivalent of getting Mexico to pay for the wall. Genius.
This is advanced politics, son. Don't make me bust the funky lyrics.