When John McCain picked Sarah Palin as his running mate, my first reaction was that the race was over and the Democrats will win for sure.

Here was my reasoning:
First, McCain has been running on the "old and experienced" ticket and now he was making a choice that would make it impossible to make such claims any more.

On top of that McCain is relatively old and not very healthy (McCain has a history of cancer and would be the oldest 1st term Prez ever) and I could not imagine that the country would be willing to take even a 1% chance that in the event that he can no longer be the president (in fact the risk might be much higher, as VPs have taken over the presidency 9 times out of 43 presidents.), the president will be someone with almost no experience.
There were other issues with this choice, but based only on these two, I predicted that the public opinion will turn against McCain rather quickly.

Clearly I was very wrong, which is just one more piece of evidence on how messed up my intuitions are. The good news is that I am sure there is an interesting research project hiding somewhere in this story.