Things right now point to Biden eking out a win - like, hitting the 270 mark exactly with Arizona, Nevada, Michigan, Wisconsin, and Maine's 2 state votes and one of their congressional districts. Hopefully, he can also flip at least one of Pennsylvania, North Carolina, and Georgia. Without that, we're looking at the tightest election in modern history (by the electoral college, at least - Biden has a significant lead in the popular vote).
Quite frankly, unless Biden sweeps all three potential swing states, it's going to be a narrow margin of EC victory - which, historically, have tended to favour Republicans - Democrats tend to win by significant margins, with the last Democratic president to win by less than 100 electoral college votes being Jimmy Carter. Meanwhile, the Republicans have won 3 elections since by that narrow a margin, and could potentially win a 4th tonight. Of course, between 1892 (when the electoral college expanded to 444 votes from 401 in the previous 2 elections, and 369 or less in all elections preceding that) and 1976, there had only been 2 other elections decided by that narrow a margin.