Apolo and Karina are in jeopardy? Oh, man. If they go home instead of Bristol and Mark, things are going to get REALLY ugly. Apolo and Karina's mistake was basically the result of a mike pac coming loose, which was not their fault, and they kept going. In fact Apolo never missed a beat. I really doubt Bristol would have been able to keep going if something similar happened to Mark.
Plus, Apolo is just obviously a lot better dancer than Bristol.