The observers must represent an eagle-eye corps dedicated to protecting voters' rights while remaining virtually invisible and avoiding actions that could be viewed as heavy-handed or intimidating.

CNN: Federal observers and monitors heading to polls

When asked afterwards if they had seen a gorilla, more than 80% of radiologists and 100% of unskilled observers, said they had seen nothing - this despite the fact that the eye-tracking monitor showed that half the radiologists who did not see the gorilla had actually looked right at it for about half a second.

BBC: Why do radiologists miss dancing gorillas?

Polling was held under the watchful eye of 47, 000 police officers and another 7, 000 election observers.

CNN: STORY HIGHLIGHTS

As speculation builds that presumptive GOP nominee Mitt Romney has his eye on the charismatic 40-year-old Cuban-American as a possible running mate, political observers want to learn everything they can about him.

CNN: Why Marco Rubio can't save the GOP