A month ago, Herman Cain edged out Barack Obama among likely voters in Rasmussen’s poll, 43/41.  Two weeks ago, before the initial allegations of sexual-harassment complaints surfaced, Cain trailed Obama by five points, 43/38 [see update].  Today, after ten days of allegations and the response from the Cain campaign, Obama now beats Cain by eleven points:

Businessman Herman Cain is losing ground in a hypothetical Election 2012 matchup against President Obama.

A new Rasmussen Reports national telephone survey of Likely Voters finds Obama earning 48% support to Cain’s 37%.  Eleven percent (11%) prefer some other candidate, while five percent (5%) are not sure.  (To see survey question wording, click here.) …

The latest survey was conducted the night prior to and of his most recent press conference.  Cain denies the newest allegations made against him, stating he doesn’t even know the woman who is accusing him of suggesting sexual acts to get her job back.  But 51% of voters nationwide now believe the allegations are at least somewhat likely to be serious and true. That’s up twelve points from a At the same time, two-thirds believe Cain’s ethics are at least as good as most politicians.

It’s not difficult to see where Cain has lost ground when looking at the crosstabs.  In October, he had a six-point lead among men and only a 4-point deficit with women.  Obama now ties Cain among men and leads Cain by twenty-one points among women, 52/31.  That’s a huge shift, one that would exacerbate a gender-gap problem Republicans routinely face in presidential elections.

The news is worse among independents. In October, Cain had a 19-point lead, 48/29, over Obama.  Today that has become a six-point deficit, 35/41.  Support from self-described conservatives in this head-to-head matchup dropped eight points from 73% to 65%, and now Cain loses every income demographic in the survey.

If it appeared that Cain’s supporers were giving him the benefit of the doubt last week, this week looks as though voters have serious questions about either the allegations or Cain’s handling of the issue.  The survey took place before the embarrassment of the false accusation leveled by Cain campaign manager Mark Block against Josh Kraushaar, too, which could mean that the campaign will have trouble reversing this momentum quickly.

Update: Cain actually first fell behind Obama before the allegations came out, and the poll I linked showed that the numbers initially didn’t move.  They moved this time.  Also, Rasmussen still shows Cain leading in Florida, but Newt Gingrich is picking up steam:

The latest statewide telephone survey of Likely Republican Primary voters shows Cain with 30% support while former Massachusetts Governor Mitt Romney picks up 24% of the vote. Former House Speaker Newt Gingrich draws support from 19% of Florida GOP voters with no other candidate picking up double-digits. …

In a three-way race between the top three candidates, it’s Cain 35%, Romney 31% and Gingrich 25%.

In a two-way race, Cain edges Romney 46% to 41%. But Cain and Gingrich are essentially tied in Florida, with the former speaker at 43% and Cain at 42%. Gingrich leads Romney 47% to 40% on a two-way ballot.

If Cain continues to stumble, those looking for a Romney alternative might need to start rethinking Gingrich.