Dem
51
GOP
49
Fundamentally, Joe Biden can go one of two routes: the northern route or the southern route. The northern route consists of trying to hang onto the so-called "blue-wall states" of Wisconsin, Michigan, and Pennsylvania. The southern route consists of Nevada, Arizona, Georgia, and North Carolina. It's all about the math. He has a lot of money, so he can advertise everywhere, but he has only so much time for campaigning, and he has to decide where to spend most of his campaign time.
Here is the final 2020 map:
In 2020, Biden got 306 electoral votes to Donald Trump's 232. However, reapportionment has cost him one EV in Michigan, Pennsylvania, and New York each, bringing his total to 303 if he wins the same states as last time. Now suppose Biden goes the northern route and loses Nevada, Arizona, Georgia, and North Carolina. This gets him to exactly 270, which is the bare minimum. If Nebraska goes to winner-take-all, that would cost him a crucial electoral vote and result in a 269-269 tie, and thus force a contingent election in the House. But it seems unlikely Nebraska will pull the trigger because then Maine will do the same thing and cancel Nebraska out, so let's assume Nebraska doesn't change the law. Consequently, just holding the three northern states will do the job for Biden. But barely.
These three states are probably easier than the southern states. In each of the northern states, Biden trails Trump by 1-2 points. That is somewhat less than in the southern states, although that changes day by day. But the demographics favor the blue-wall states. They are heavily populated by older and whiter voters, many of whom are union members. Biden is doing well with these voters, and they are largely on his side on Middle East policy. The southern states are younger and browner, and Biden is losing support with those groups.
Now consider what happens if he loses the three blue-wall states but holds Nevada, Arizona, and Georgia (without picking up North Carolina). We start with 303, then subtract 10 (Wisconsin), 15 (Michigan), and 19 (Pennsylvania). This gives Biden 259. That's clearly much worse.
Basically, the blue-wall states have more EVs and are also demographically more friendly. Georgia will be especially tough with no Senate race this time. However, Arizona will have a bitterly contested Senate race and that may help Biden. If he loses Wisconsin but holds Arizona, together with Michigan and Pennsylvania, he still wins. In any event, Biden campaigning in the blue-wall states seems like a better bet and Biden is probably going to do that. (V)