Can’t do a small thing, so certainly can’t do the bigger thing
I can’t remember my first kiss, let alone if it was any good.
We don’t have enough money for a hamburger, let alone steak.
He can hardly speak English, never mind Chinese.
I didn’t notice you had gone, never mind cared.
His cat can hardly walk down the stairs, much less catch a mouse.
The voters didn’t like his appearance, much less his policies.