The last we saw of South Carolina polling three weeks ago, Newt Gingrich had a large lead over Mitt Romney, the only two candidates in double digits, and Rick Santorum tied Jon Huntsman for last place.  My, how things have changed over the Christmas holidays.  After their dead-heat finish in Iowa, Mitt Romney and Rick Santorum now lead the latest Rasmussen poll 27/24, respectively, and Gingrich has dropped to 18%:

What a difference a caucus makes. Rick Santorum who two months ago had one percent (1%) support among likely South Carolina Republican Primary voters now is running a close second there with 24% of the vote.

The latest Rasmussen Reports telephone survey in the Palmetto State finds former Massachusetts Governor Mitt Romney still in the lead, earning 27% support from likely GOP Primary Voters, up from 23% in early November. Former House Speaker Newt Gingrich is in third with 18% of the vote, followed by Texas Congressman Ron Paul at 11%.

Bringing up the rear are Texas Governor Rick Perry with five percent (5%) and former Utah Governor Jon Huntsman at two percent (2%). Another two percent (2%) of these likely primary voters like some other candidate, and 11% remain undecided.

Ron Paul doesn’t appear to have gained a lot of traction in the same period.  The RCP average had Paul at 8.5% for December before today’s Rasmussen poll, but the mid-month Clemson poll had him at 10%.  His surprising drop in Iowa to third place has not hurt him, but he’s not picking up any momentum, either.  Rasmussen’s sample is 74/26 Republicans to independents, so it isn’t as if the survey of 750 likely primary voters (conducted in its entirety yesterday) tried to avoid Paul’s base, either.

Looking at the internals, Santorum competes better in some demos with Romney.  He edges Romney among men, 27/25, but is behind 30/20 with women and almost tied with Gingrich at 19%.  Surprisingly, Romney edges Paul for voters under 40, 25/22, with Santorum in third at 16%.  Santorum tops Romney with 40-64YOs 30/22, but Romney wins seniors by a large margin, 41/25 over Gingrich, with Santorum in third again at 18%.   Romney and Santorum win among Republicans and non-Republicans, 29/25 and 23/21, respectively.  Paul only manages a 19% with independents and just 8% among Republicans.

Romney has a bigger problem with very conservative voters.  He comes in third among this self-identified set, which comprises the plurality in the sample (41%), behind Santorum (36%) and Gingrich (22%).  Santorum has a problem among “somewhat conservative” voters, as Romney wins 38% and Gingrich comes in second at 20% among respondents who accounted for 35% of the sample.  Santorum will have to find a way to increase his appeal beyond the very conservative base, while Romney has to work in the opposite direction.

Santorum may have the edge in making that case.  His favorability rating is 72%, a bit higher than Romney’s 68% and Gingrich’s 59%.  Romney gets a 65% favorability among very conservative voters, but Santorum has a 74% rating with somewhat conservative voters, so he has more potential upside in the demo he needs to target.  Paul’s favorability is only 39%, which beats Jon Huntsman’s 29%.  Rick Perry gets to 50%, but only 9% find him “very favorable,” which portends a very poor showing for the Texas governor in a couple of weeks.

The news has to be encouraging to both Romney and Santorum.  Romney was not expected to do well in South Carolina, but his numbers have improved quite a bit over the last three weeks, and two-thirds of voters in this poll expect him to win the nomination, while 45% believe he’s the strongest candidate to beat Obama in the fall.  Only 16% believe that of Santorum, which means his support outstrips his perceived viability.  A second-place finish in New Hampshire might improve that number and perhaps add more to his support, but that may come at the expense of other conservatives in the race rather than Romney.