Today's Gallup tracking poll puts Rick Santorum at 34% of the vote and Mitt Romney at 30%, but the narrowness of that four point gap understates the magnitude of Romney's challenge of breaking down the Not Romney coalition that once consisted of five candidates—Herman Cain, Michele Bachmann, Rick Perry, Newt Gingrich, and Santorum—but now just consists of two.
As you can see from this chart, in mid-January it briefly appeared that Romney had broken through his ceiling, but a month later, things are almost back where they started at the beginning of December.
Source: Gallup daily tracking poll
The good news for Romney is that although the trend has been good for him since mini-Tuesday, he's still narrowed the gap from a 31 points in early December to 18 points today. The bad news is that his 18 point gap is still bigger than it was at the end of December—and today he's facing just two candidates, one of whom he trails, instead of four candidates, all of whom he led.
In the last Gallup tracking poll taken entirely in December, Romney's total support was 26 percent. Today, it's 30 percent, a gain of 4 points. But Newt Gingrich and Rick Santorum had a combined 29 percent back then and today they are at a combined 48 percent—a gain of 19 points. Not only did virtually all of Rick Perry's and Michele Bachmann's support (which stood at 12 percent) go to Gingrich and Santorum, but they have picked up some undecided supporters as well.
None of this means that Romney is toast. Predicting how this Republican clown show will play out is essentially impossible. But Romney should be proud of at least one thing: given that he's the father of Obamacare, he's actually doing quite well.