He could be a spoiler hard to say.
Instead of the obvious spoiler role as currently an Independent, if Bobby can coax Ds into putting him on the ticket, Trump could beat him one on one. Otherwise I think Kennedy would draw votes like Ross Perot to hand it to the D.
Rs can work on securing the voting system, campaigning not only for Pres but getting majorities in both houses of Congress. They should also work on choosing better people to be the R “Leaders” (Turtle and Johnson are highly compromised, defective and feckless).