Great question!
Cain does not have the money to fight a marathon. On FR we get all kinds of info and discuss it, but we are more the exception than the rule. The vast majority of voters will start making decisions based on advertising. He doesn't have the money for it.
Also, Cain is very popular right now because he "shoots from the hip". However, I am convinced that after the last 3 yrs of obama voters want competent leadership. The Pubs in the primaries are placing a high priority on electability.
Cain has also exhibited a profound lack of understanding how govt works and what you need to do to get things done.
He has not responded well to what social conservatives place a priority on. He failed to sign a Pro-Life pledge and then tried to explain this away on the basis that the POTUS can't advance a bill. His backing of Pro-Family issues is questionable.
The value of Sarah Palin supporting him would probably be off set by those who will not support him because of it. If she came out in support of Cain he would get a huge bounce, but would be further marginalized in the process. Palin's power to sway a majority of the American people is over estimated.
The Perry factor is also at work in the sudden explosion of support for Cain. Cain's rise in the polls corresponds to Perry's decline. Perry did not do well at the 2nd & 3rd "gotcha" panels and his ratings declined. If Perry shows improvement at the next couple debates the luster on Cain dims. Perry does not tend to "shoot from the hip", he has executive experience as Gov. of the 2nd most populous state in the country, he has a solid organization and is raising 6X's the amount of money Cain is raising and is a solid conservative on the social issues.
Thank you for sharing your insights, dear wmfights!