Robert F. Kennedy Jr. has found himself caught up in an explosive legal battle stemming from a secret romance he allegedly had with New York Magazine writer Olivia Nuzzi. RadarOnline.com can reveal the latest twist in the love triangle saga saw Nuzzi, 31, claim she was subjected to harassment and blackmail by her ex-fiancé, political journalist Ryan Lizza. In her complaint, Nuzzi alleged: “(Lizza) explicitly threatened to make public personal information about me to destroy my life, career, and reputation – a threat he has since carried out.” She alleged this behavior by her ex, Politico’s chi…