Bear in mind Tina’s caveats about the difficulty of polling in the holiday season, but this does look as though the predictions of Rick Santorumentum have been realized. In the latest Rasmussen poll of 750 likely caucus-goers in Iowa, conducted yesterday, Santorum leaps up to third place, behind a virtual dead heat between Mitt Romney and Ron Paul:

After months of volatility, Mitt Romney and Ron Paul remain the front-runners in Iowa for the third week in a row with the state’s Republican caucus just five days away. The latest Rasmussen Reports telephone survey of likely GOP caucus participants finds Romney with 23% support to Paul’s 22%. Former U.S. Senator Rick Santorum has moved into third place with 16%, his best showing to date, closely followed by former House Speaker Newt Gingrich and Texas Governor Rick Perry who earn 13% of the vote each. Minnesota Congresswoman Michele Bachmann picks up five percent (5%) support, while former Utah Governor Jon Huntsman gets three percent (3%) of the vote, marking no movement on either candidate’s part over the past week. One percent (1%) like some other candidate, and six percent (6%) are undecided.

That’s a six-point jump for Santorum in one week, outside the margin of error. In contrast, Romney and Paul both only shifted within the MOE to get closer together. Perry also added to his total by three points, again within the MOE, while Gingrich dropped four points in the same period to fall into a tie for fourth place.

The sample improves over the CNN poll, which only surveyed Republicans. According to the sample data provided by Rasmussen, 30% of respondents are independents, a good representation. None are Democrats, though, who could cast votes in the caucus, and who thus far favor Paul. The survey was taken in a single day, which sometimes makes the results a little less reliable, but I believe the Rasmussen polls in this series have all used that methodology, so the trending is still significant.

Where does Santorum pick up his support? He comes in second to Romney among Republicans, 26/19. He falls into a three-way tie among women, far behind Romney, 27/15, and third among men at 17%, with Paul leading Romney 27/19. Santorum has a double-digit lead among very conservative respondents over Romney, 28/18, but lands in fourth place among “somewhat conservative” voters at 15%, behind Romney (27%), Paul (18%), and Gingrich (17%). Santorum also leads among Tea Party adherents, 25/19 over Romney, with Paul fourth at 14% behind Perry’s 15%, and Santorum wins evangelicals with 24% to Perry’s 17%.

Is that enough to ignite Santorum for a win? He may not need an outright win. As long as he bests Perry, Gingrich, and Bachmann, Santorum could be a rallying figure for social conservatives and evangelicals, which would stand him in good stead in South Carolina. It’s still a long shot, but it’s not out of the question.