Reality Check
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.
Giuliani 28%
Thompson 19%
McCain 13%
Romney 12%
Huckabee 10%
Paul 5%
Tancredo 2%
Hunter 1%
Other 2%
No Opinion 8%
In comparison, the current RCP average (note, this is a dynamic page and the data may change on later readings) is:
Cain 25.5%
Romney 23%
Gingrich 11%
Perry 9.8%
Paul 8.2%
Bachmann 3.5%
Santorum 1.5%
Huntsman 1.2%
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.