While Biden's win was impressive, …
It wasn’t impressive.
Typically, an opposition-party challenger who unseats and incumbent U.S. President experiences a minimum of a 10-point national shift with percentage-points margin in the U.S. Popular Vote. Had 2016 Republican pickup winner Donald Trump won the U.S. Popular Vote, his margin would have reached +2. (I estimate +2.15 to +2.64.) Figure…one net gain in flipped states with each percentage point nationally shifted to that Republican or Democratic pickup winner. (Trump, following 2012’s Mitt Romney, flipped six states—including four of the nation’s Top10 populous states—and a congressional district which is nearly half its statewide vote.) 2020 Democratic pickup of the presidency, following an adjusted 2016 U.S. Popular Vote margin of –2, should have reached approximately +8 percentage points. (A national margin of +8 for a winning Democrat would be 29 or 30 carried states.)
Joe Biden did not perform impressively. He got by. (And with a pandemic having struck on the watch of incumbent Trump.)
Most losing incumbents don't have an approval rating around 45%. It was just a few points lower than Obama and W Bush. Carter and HW Bush, who did lose in landslides, had approval ratings in the mid to low 30s. The closest comparison is Gerald Ford, who was in the same range as Trump and barely lost. The reality is that Biden couldn't have done much better because there was a hard floor of people who positively approved of Trump, for some mystifying reason.
