"He wasn't wearing one of those hats, was he? And he never will, and that's OK because we got to do something folks because it's not working," said Trump, pointing to the crowd and referring to the protestor.
In the last few months, before Trump takes the stage an announcement is read telling Trump's supporters to "not harm a protestor" but instead to chant "Trump, Trump, Trump," as an alert to security that a protestor has been spotted. The crowd roared Sunday after the protestor was escorted out and shouted "USA, USA, USA".
Trump is campaigning in Iowa ahead of the next week's crucial caucus. Latest polls showed that he has taken a lead over his nearest Republican rival Ted Cruz. Iowa Caucus on February 1 is considered crucial as it would set the trend for the rest of the presidential primaries over the next few months.