Billionaire businessman Donald Trump refused to rule out running for the White House as an independent, during the first TV debate for Republican candidates.
The Cleveland event ended speculation that the controversial tycoon would moderate his harsh denouncement of US politicians.
If Mr Trump runs as an independent he would probably split the Republican vote, making it more likely that Democrat frontrunner Hillary Clinton would win, giving her party a third straight term in the White House.
He was the only one of 10 candidates in the debate to raise his hand when asked who would not pledge to support the eventual party nominee. "I will not make the pledge," he said.