When was the last time that a Presidental candidate picked an expected VP? I don't remember.
Cheney certainly wasn't expected. Lieberman was on short lists, but I believe usually as a second tier possibility. Clinton picking Gore, which I remember as being surprising. Quayle was a complete surprise. Bentsen? The first George Bush was perhaps the last obvious choice that became the VP choice.
So, my point is that campaigns try to surprise with their VP pick and we shouldn't get too caught up in what we think is going on.