A man who has spent a lot of time with Donald Trump explained on Saturday how he thinks Vice President Kamala Harris is getting under his skin. Trump biographer Tim O’Brien, author of TrumpNation: The Art of Being The Donald, appeared on MSNBC over the weekend to discuss the former president and the upcoming election. Earlier in the interview, O’Brien noted that Trump could lose half of his entire net worth if he doesn’t win back the presidency in November. After that portion of the interview, O’Brien was asked whether or not Harris got under Trump’s skin at the Democratic National Convention….