By that logic though, the April calendar is tougher and could trip up Santorum. April 3rd is WI, MD and DC, so he's really got to win WI or he looks really weak, with a 3-week gap then until the mini-Super Tuesday on April 24th. NY, CT, RI and DE are probably all going to be Mitt wins. Santorum better get PA, but he is likely to end up looking about as strong as Newt did on Super Tuesday, only winning his home state. The calls for Rick to drop out of the race by the RINO media and GOP elite will be deafening at that point, knowing that May looks like a much weaker month for Romney. I do wonder if LA showed us that the increasing focus on Obamacare in the media is going to hurt Massachusetts Mitt. That could help Rick in WI. Apparently the decision's not coming out until late June so it probably won't continue to be the top media issue after the April 3rd primaries.
The whole Santorum campaign is premised on him winning WI. Without that, there is really no way for him to seize enough momentum to crush Romney. The thing is that most of Santorum’s wins from here on out need to be crushing, while Romney’s need to be much closer. If Santorum can crush Romney in PA (20+ points, more preferred), and then maybe pickup DE, and hold Romney below a majority in NY, that will put him in pretty good shape for May, when only Oregon should show much promise to the Romney campaign.
Preventing Romney from winning outright is going to be a close call unless some massive scandal erupts or momentum shifts in a massive way. However, it is still not in the realm of the impossible.