Reading from his Twitter account at an event in Iowa, Donald Trump defended not correcting a questioner who challenged President Barack Obama's citizenship and said he was a Muslim at an event in New Hampshire earlier this week.
"Am I morally obligated to defend the president every time somebody says something bad or controversial about him? I don't think so!
"This is the first time in my life that I have caused controversy by NOT saying something.
"If someone made a nasty or controversial statement about me to the president, do you really think he would come to my rescue? No chance!" Trump posted on Twitter.