Click here to view this media The country's most prominent Republican birther says that one of his party's early frontrunners for the 2016 presidential nomination may "perhaps not" be eligible to run if he was born in Canada. In an interview that aired on Sunday, ABC's Jonathan Karl reminded billionaire Donald Trump that his false claim that President Barack Obama was not born in the United States made him appear "not serious." "You don't still question whether he was born the United States?" Karl wondered. "I have no idea," Trump said.