The origin of the error comes here: Newsmax: Rasmussen: Obama Leads...
It appears someone at Newsmax left a paragraph sitting around in their story, refering to the old poll. The last paragraph reads:
Among likely GOP primary voters nationwide, Romney is just behind businessman Herman Cain with 23 percent support; Cain earns 26 percent of the vote and Former House Speaker Newt Gingrich is in third with 14 percent support. Romney runs best in New Hampshire – where he picks up a commanding 41 percent of the vote -- but falls short of Cain in Iowa, South Carolina and Florida.
So it appears that the Cain campaign has NOT subscribed to Rasmussen's feed (if they did, they'd get their information directly), and instead of checking with Rasmussen, they reacted to a Newsmax story.
I love Newsmax -- but I will tell you that I wouldn't generally count on it directly. Go to the source material. I wouldn't make this mistake in my local opinion column. College students are taught to go to original sources. But sending out a donation e-mail using faulty information is a pretty rookie mistake.