US Republican presidential frontrunner Donald Trump says he would not rule out running as a third - party candidate if the GOP establishment treats him unfairly. “I’m going to have to see how I was treated... It’s not a question of win or lose; it’s a question of treatment,” Trump said on Fox News Sunday. “I’m by far the front-runner. I want to run as a Republican. I will beat Hillary Clinton,” the celebrity businessman added. Trump expressed concern that the Republican Party might try to “steal” the nomination from him if he fails to win the 1,237 delegates necessary to clinch the nomination. In September, Trump signed a pledge to support the eventual Republican nominee, but backed off that promise on Tuesday. The real estate magnate has previously said that “so many people” would want him to run a third-party campaign if he does not secure the GOP nomination. Observers say that Trump may finish about 80 delegates short of the absolute majority, meaning that the Republican National Convention in July will start without a presumptive nominee. In that case, campaigns will jockey for advantage and either change or uphold the rules that have governed the primary up until that point. There might be several ballots. Most delegates are pledged to their respective candidates for the first ballot. After that, they can vote for other candidates. Trump has propelled himself as the GOP frontrunner by framing himself as an anti-establishment outsider. However, his campaign has been defined by controversy from the beginning, including disparaging remarks about women, immigrants and Muslims.