By the looks of it, Gingrich is reducing his campaign staff by 1/3, which leads me to believe he'll effectively drop out soon. This improves the field on the national question (Santorum is A-, Romney B-, Paul D- on the national question per numbersusa.com).
There's another encouraging angle I hadn't considered until today, although Steve Sailer has mentioned it quite a few times in other contexts. The last 3 presidents have had only daughters, no sons. Santorum, Romney, and Paul all have sons, quite a few of them in fact between them---Romney has 5, Paul has one who is a senator, and Santorum homeschooled all his. They are therefore inclined to at least consider the interests of their sons and grandsons in making decisions.
Lastly, those gasoline prices I often talk about are creeping past $4/gallon throughout much of the US, and peak prices for the year aren't here yet (usually late April is when that comes). Such prices are brutal to the incumbent party in elections.