A lot of these "who runs in 2028" questions are hard to answer until we know whether Trump or Biden wins in 2024. I'd strongly suspect that whichever already unpopular candidate wins in 2024 will be even less popular in office. My "prior" is that the losing party in 2024 has at least a 75% chance to win in 2028. So, more serious candidates will give it a go if they think the election favors their party.
Biden will be Bush 43 2nd term levels of unpopular for sure but Trump might benefit from the expectations being reset (even though he'll likely start with at least 40% of the country hating him).
Also might not matter in his case cause project 2025.
