Watch | Donald Trump assures America he is well-endowed

Trump opened the Republican debate on Thursday night with his devastating response to Marco Rubio joking about the size of Trump's hands and saying “you know what they say about men with small hands.”On the debate stage, Trump stretched his hands out for the audience to see - then insisted that the suggestion that “something else must be small” was false.“I guarantee you there's no problem,” Trump said to howls from the audience at the Fox debate.In fact, Trump fielded attacks from Ted Cruz and Rubio throughout the night.