The "Pence" we see now is almost certainly a body double. He was swapped out at the end of 2017 (if not before). Biden was switched in Nov 2017. Check out early videos and you'll see the slight differences - ears especially.

Most people's facial recognition skills aren't perfect. Many suffer from slight prosopagnosia* so when presented with a person, they tend to rely on other clues. If he dresses the same, has similar hair, accent and appears in the place they expect, then people just accept that it must be him.

Most "identical twins" aren't completely identical but, if you see just one of them, you'll struggle to decide which one it is (assuming no obvious scars or tattoos and that they always dress the same).

• from the Greek "prosopo" meaning "face" and "agnosia" meaning literally "not knowing" (specifically in reference to a person rather than a thing or fact).