Just as reference, here are the results from the November 8, 2007 Gallup poll of Republican candidates. The past is not the future, but it’s useful to keep it in mind.
No Opinion 8%
In comparison, the current RCP average (note, this is a dynamic page and the data may change on later readings) is:
It is my personal opinion that anyone with numbers below Paul can be ignored, but everyone having higher numbers could turn out to be the nominee once all the failing is done.