Julian Zelizer at CNN:Donald Trump has suggested, in an interview with The Hill, that if the Republican Party doesn't treat him right, he might run as a third-party candidate. Republicans should be worried.
If Trump takes this step, he would add a serious element of uncertainty into an already unwieldy process. Trump can bring his demagoguery and willingness to say anything approach to the general election, when the outcome in a handful of states will determine the next president. [...]