Given the current state of partisan polarization, it’s unlikely Biden can get majority job approval next year even with the most fortunate set of circumstances. But the good news for him is that he probably doesn’t have to. Job-approval ratings are crucial indicators in a normal presidential reelection cycle that is basically a referendum on the incumbent’s record. Assuming Trump is the Republican nominee, 2024 will not be a normal reelection cycle for three reasons.
The worst possible timeline is if Biden wins the election, but croaks before the election can be certified by Congress. There will be legitimate challenges over whether any Biden/Harris electors can be accepted at all, and the election may go to the House/Senate to decide. And even if the Democrats control Congress , if the House has to vote on who should be President each state’s delegation gets 1 vote, and that math favors Republicans.
In that scenario, a Trump/Harris administration is extremely likely, even if the Biden/Harris ticket won enough EC votes to win.