The above posts list some bad running mates, but honestly, did any of them LOSE the election for the top of the ticket? I doubt it.
Nobody was going to beat Obama. I could run LITERAL JESUS against Obama and he’d have lost. Obama was practically the perfect candidate. Palin wasn’t a good running mate, but she wasn’t the reason McCain lost.
I think VP candidates just don’t move the needle that much. They can hurt a bit or help a bit…but only so much. And most races aren’t really that close, and few swing voters are going to base their decisions on the VP. Like Adams said of the job: ”...the most insignificant office that ever the invention of man contrived or his imagination conceived.” And I think the voters mostly understand that.