Priebus' use of the #NeverClinton hashtag indicates a major shift in the election and demands the GOP now focus solely on the assumed Democratic nominee.
Trump has had a love-hate relationship with the RNC throughout the 2016 primary. First, at an early debate, he refused to sign a pledge to support the Republican nominee if it wasn't him, then he signed the pledge, then he refused to honor it. Through all the flip flopping, Priebus didn't know what to make of him. Moreover, Trump called the Republican primary process "rigged" after losing delegates in state conventions where average voters didn't have a say.
Now, however, the chairman has acknowledged it's time to make friends with the bombastic businessman.