Donald Trump Jr. said Sunday he's open to running for public office some day — quoting his father's advice that ""we always like to keep our options open."In an interview with CNN'sthe eldest son of GOP presidential nominee Donald Trump said his "100 percent focus" is to help his father win in NovemberWhen pressed by host Jake Tapper if after the election, he might consider a run against liberal Democratic New York Mayor Bill de Blasio, Trump Jr. left the door wide open."I never like to rule anything out," he said. "As my father has always said 'we always like to keep our options open.' If I can do that as a service to our country, I'd love to do it."The younger Trump also laid into Robby Mook — Hillary Clinton's campaign manager — for suggesting thefrom the Democratic National Committee."It's so phoney," Trump Jr. said, referring tothat experts believe the Russians are behind leak."I can't think of bigger lies, but that exactly goes to show you what the DNC and what the Clinton camp will do," he said. "They will lie and do anything to win. You hear it with the DNC where they're leaking e-mails about Bernie Sanders and his Jewish heritage, to be able to try to try to destroy him in the South. It's a rigged system, it's disgusting and the people who should be fed up because when I heard it I certainly was.""I don't mind a fair fight, but these lies and .... nonsense to try to gain political capital is just outrageous and he should be ashamed of himself."The Trump scion also shot down suggestions that former Fox News CEO"I know they are friends and have a long-term relationship but I'm happy with the work [campaign manager] Paul Manafort is doing," Trump Jr. said. "I think our team is coming into place… it's been exciting to be a fly on the wall watching a lot of this stuff go down."