i have always assumed he'd run and win by a ton, but i think this is a good point. antivaxxers are a significant number of his voters and it could trigger some outsized reaction from them.
one other thing is i've never seen numbers that articulate who his voters were in 2016 versus 2020. 8 years between 2016 and 2024 is a long time. with an 80 year life span, it seems to imply 10% of his 2016 voters will be dead by then, 5% of his 2020. was the increase between 2016 and 2020 just the same demographic profile as the original 2016 R voting bloc(k), just four years older? or was he able to backfill effectively with yoots, who cannot be counted on to die by 2024. i assume the big jump in D votes were spread throughout the age brackets.
(as i'm writing this, i just googled the answer; at least a good substitute to it in contemporaneous self-identification of party. it looks like trump's voting base just aged and he didn't back fill with kids. biden did fine with kids. i think that is the most positive thing i've seen to make me think trump won't win again in 2024)