Donald Trump unleashed attacks against Robert F. Kennedy Jr., a longshot independent candidate, on Friday.Alex Wong and Tayfun Coskun/Getty ImagesDonald Trump posted on Truth Social Friday about Robert F. Kennedy Jr.Trump called the third-party candidate a "Democrat 'Plant'" and "Radical Left Liberal."The diatribe comes as polling shows RFK Jr.'s run could siphon votes away from Trump.Donald Trump will likely face a second contest against Joe Biden in the upcoming election, but the former president has another candidate currently in his crosshairs.On Friday evening, Trump took to Truth Social to attack Robert F.