I looked at this earlier and wondered about 'winner' myself but couldn't see it. Sammy's posting prompted me to look at it again and I wondered about the following explanation:
'to back' = o (i.e. the back of to) + winner = owinner. If you dismiss 'in' (= now) it leaves owner.
It's the last bit which might be tenuous - 'in' could be in the trendy sense i.e. currently or now popular.
Best I can come up with anyway.