The Des Moines Register is out with a new poll of likely caucus-goers. Herman Cain (23 percent) and Mitt Romney (22 percent) are in a statistical dead heat. Far back is Rep. Ron Paul (R-Tex.) at 12 percent. Then come Rep. Michele Bachmann (R-Minn.) at 8 percent, Newt Gingrich and Texas Gov. Rick Perry at 7 percent and Rick Santorum at 5 percent. There is plenty to chew on.

We should begin with a word of caution. The poll has a margin or error of plus or minus 4.9 percent. That means Romney might be ahead or Santorum could have passed Bachmann. Moreover, there are a ton of debates and plenty of retail politicking an TV ads between now and the Iowa caucuses Jan. 3. This is at best then, a blurry snapshot in time.

With that in mind, what can we learn? Strikingly, Cain is not suffering from his near-total absence from the state. Perhaps he is simply, for now, the main vessel for the not-Romney votes. What is clear is that the other not-Romney candidates have erred in not taking Cain on earlier and more vigorously. Perhaps Cain’s numbers are “soft,” but unless Bachmann, Perry and Gingrich alter the race’s dynamic, all three could see whatever chance they have for the nomination evaporate in Iowa.

Meanwhile, Romney has not been hurt by his absence from the state, either. (“Romney has campaigned in Iowa just three times this year and skipped the Iowa straw poll in August. Cain has visited only once since the straw poll. The message to candidates seems to be: The less you’re here, the more we like you.”) He chugs along with essentially the same bloc of 20 to 25 percent of the Iowa vote he’s had since 2008. So long as he keeps those voters, the potential for a surprise win remains. Moreover, anyone who is going to top him is going to have to corral north of 20 percent of the vote. That is a steep hill for those mired in single digits.

The poll also raises a question as to why media continue to treat Perry as a first-tier candidate. He’s within the margin of error — with Santorum, for goodness sakes. The poll ran from Oct. 23 to 26, right after Perry made a big speech introducing his new economic plan. There is zero evidence so far that his new flat-tax proposal or his millions in fundraising (surely bleeding away with an army of new advisers and a TV campaign) have made any difference. Unless he sees significant progress soon, he’s headed for a humiliating loss in Iowa and a quick end to his nomination prospects.

Gingrich, Bachmann and Santorum are in a virtual dead heat. All have spent significant time in the state. All can compete for Cain voters. If one of them can break free of the pack and make a run for third place, he or she will be the “surprise” story line and continue to contend seriously for the not-Romney position.

So far Santorum’s Web ad is the only effort to go after Cain with gusto. The other contenders for the not-Romney vote should readjust their sites. Cain may be a candidate with serious flaws. He may not have staying power after Iowa. But he has the power to send them all home. If they want to get a ticket out of Iowa, they better figure out a way to puncture the Cain bubble.