FLASHBACK APRIL 2007 (IOWA POLL)
http://news-releases.uiowa.edu/2007/april/040307poll-data.pdf
DEMS
Clinton 25.5
Edwards 23.2
Obama 16.3
REPS
Guliani 17.5
McCain 14.4
Romney 9.6
There is a lesson to learn in early polling data. It will always be wrong.
The poll cited from 1992 was not an early poll. It was June of 1992 after the two major party candidates had been chosen in the primaries. It's the equivalent of June 2012.
You're citing polls (April of 2007) more than a year earlier in the election cycle than the NYT poll with Perot. Bush and Clinton.