I seriously doubt that. People who vote for RFK Jr. are unlikely to have voted for Trump anyway. Ergo, he will hurt Biden more. The Democrats know that too which is why they’ve been trying to keep him out of the debates, off of TV and off the ballot in key states.
Oh please! The legal battles to keep Kennedy off the ballot are simply how they’ll allow him to run in the states where he can hurt Trump and keep him from running in the states where he can hurt Biden.