I think it's more that the Romney-Gingrich dustups have consumed all the available media attention, and in doing so kind of leave Santorum and Paul on the sidelines, going "Hey, we're still an option too, y'know!"
It's like you have to constantly remind me people that they have more than two candidates to choose from, or else they just completely tie into the "pick your side" 1v1 contest. Kind of a tangent here, but I've always felt that our affinity for the two-party system was dramatically entrenched by the Cold War and the bipolar worldview it created. Us v Them. Americans have a real hard time with multipolarity and shifting alliances. But if you look prior to WWII (especially the latter half of the 19th century), we had a number of significant third parties. Postwar, almost none of note.
I never thought I'd say this, but I'm grudgingly coming to respect Rick Santorum as a person. Not as a politician, mind you; and gods know I wouldn't vote for him in a million years. But here's the thing: he's run a clean, old-fashioned kind of campaign. No blitz of negative ads, no jet-setting all over the country, no big flashy photo ops, no spin doctoring. He's putting in the hours going door-to-door, speaking at the Rotary Clubs and town halls, and for the most part he's stuck to his guns, foul and bigoted as they may be. Kinda reminds me a bit of Jesse Helms in that respect. You might have hated the man, and he might have hated you, but at least he was open and honest about it.