Donald Trump’s campaign for the Republican presidential nomination seems to defy gravity and all the other laws of nature.He insults Mexicans, military veterans and women, and makes taunting remarks about the bodily processes of popular TV host Megyn Kelly. His poll numbers remain steady or even increase.The Republican Party establishment, the pundits, the Fox News management and conservative hotheads like Erick Erickson deride Trump and try to knock him out of the race. He still runs way ahead of everybody else.Is there anything Trump could say that is so outrageous it would cause supporters to desert him?