On 11/11/11, Herman Cain's lead dropped by 11 points in Iowa.

Levity aside, amid the sexual harassment allegations that have engulfed Cain's campaign since Politico first published them on Oct. 30, his healthy 15-point lead over Mitt Romney in Iowa last week has become a shaky 4-point advantage, and he has fallen into third place in one national poll.

According to an Insider Advantage poll conducted on Tuesday, Cain had 23 percent support among likely Republican voters in Iowa, and Romney had 19 percent. Newt Gingrich was in third place with 15 percent, followed by Ron Paul with 11, Rick Perry with 9, Michele Bachmann with 5, Rick Santorum with 3 and Jon Huntsman with less than 1 percent. The margin of error was plus or minus 4.6 percentage points, putting Cain and Romney in a statistical tie.

By contrast, an Insider Advantage poll conducted on Nov. 3, just five days earlier, showed Cain with 30 percent support, Romney with 15 percent, Gingrich with 12, Paul with 9, Bachmann with 8, Perry with 6, Huntsman with 2 and Santorum with less than 1 percent.

Nationally, a McClatchy-Marist poll also showed a significant drop for Cain, who fell into third place with 17 percent support. Romney led with 23 percent support and Gingrich moved into second with 19 percent, with a margin of error of plus or minus 5.5 percentage points.

But at the same time, a CBS News poll showed Cain in a statistical tie for first place with 18 percent support nationally, followed by Romney and Gingrich with 15 percent each. The margin of error was plus or minus 5 percentage points.

The disparate results of the CBS and McClatchy polls and their relatively high margins of error make it difficult to say just how much the harassment allegations have affected Cain's popularity. But the fact that some polls are showing significant decreases for Cain is a worrisome sign, given that he was almost invariably in first or second place throughout October.