Today, I'd say it's Biden's to lose. I think he's a buffoon, but people dismiss how hard it is for a sitting President to lose.
Something bad has to happen and it typically has to happen late in their term.
Trump had Covid.
H.W. Bush had a rapid recession come out of nowhere with double digit unemployment....if memory serves, the recession was over before Clinton even took office.
Carter....gas shortages, hostage fiasco and inflation/massive interest rate spikes.
Hoover.....the Great Depression.
That's it, in the last 100 years we've had 4 elected Presidents that have lost their bid for re-election.