What does a narrow second-place finish get you in national polling?  A solid bounce to second place, if you’re Rick Santorum.  The latest Rasmussen national poll puts Santorum firmly into the top tier:

Former U.S. Senator Rick Santorum, coming off his photo finish with Mitt Romney in the Iowa caucuses, is now in second place among Republican voters in the race for the party’s 2012 presidential nomination.

The news for the rest of the field, save Mitt Romney, is less than stellar:

The latest Rasmussen Reports national telephone survey, taken the night after the caucuses, shows Romney again in first place with support from 29% of Likely Republican Primary Voters, followed by Santorum with 21%. Former House Speaker Newt Gingrich, who led the pack in late November with 38% of the vote, now runs third with 16%. Texas Congressman Ron Paul, the third place finisher in Iowa, picks up 12% of the vote, up from eight percent (8%) in the previous survey.

The two remaining Republicans in the race, Texas Governor Rick Perry and former Utah Governor Jon Huntsman, each earn four percent (4%), marking essentially no change from late November.

Santorum rose 17 points in the last month, rocketing to the position of the latest Not-Romney as support for past holders of that position dwindled substantially.  But he’s not the only one benefiting from a surprisingly good performance in Iowa.  Romney’s stock has risen by 12 points in the same period.  His favorability has barely changed, from 67% to 68% over that time, so it appears that Romney may have benefited from the exodus from Gingrich.  Gingrich, bt the way, has dropped nineteen points in favorability in the last few weeks since the previous survey, a precipitous fall that explains his current position in the field.

Rick Perry may have decided to keep going to South Carolina, but he won’t get much of a lift from this survey.  He’s in the exact same position as in late November, even with Michele Bachmann out of the race.  Interestingly, Ron Paul has fallen to fourth place but has more support at 12% than he did tied for third at 8% in the last survey.

Rasmussen’s sample looks pretty solid, with 73% Republicans and 27% independents among 1,000 likely primary voters.  The internals of this poll look pretty good for Romney, however.  He and Santorum finish first and second among men (29/19), women (30/24), and every age demo except 18-39YO, which goes Romney/Paul 34/18, which is bad news for Paul — although Rasmussen has consolidated its traditional age demos into fewer categories, it should be noted.  Santorum gets a third of “very conservative” voters, with Gingrich in second (33/25) and Romney in third at 18%.  It’s Romney/Santorum among “somewhat conservative” voters (33/21), thouggh, and Romney/Paul (36/17) among “other”.   Romney’s still winning the independents at 25%, with four candidates tying for second place, as well as the Republicans, 31/23 over Santorum in second place.

It looks like Santorum’s bounce is both wide and deep, but not enough to overpower Romney, at least not in a crowded field.