I fear this is not good news for Trump. It introduces a far greater amount of unpredictability AND it also provides another path for fraud because he will probably be in the double digits.
His candidacy may be much like Ross Perot’s was and we all know how that worked out.
Difference is that Perot was the populist and Bush was the conservative. Kennedy’s a global warming cultist so will more likely pull more votes away from Biden (unless they replace him) than from Trump.