First of all, those organizations don't necessarily have any support in these particular states much less enough to turn the vote.
Secondly, why would they want to stop Romney? They totally have him beat and know it.
I think the reason Rick & Newt picked up so much support in the 11th hour was the candidate forum in AL. Romney pretty much said he didn't have time for their little hillbilly affair and (thanks in part to Freepers) it ended up being televised. Romney hadn't counted on that, was told it wouldn't be televised if he wasn't in it. Anyway, I know if I lived in AL or even MS and got dissed like that it would influence my vote.
There were even robocalls going out for dems to vote for Santorum. Kos and Huffo are as influential with Dems as Rush and Hannity are with Conservatives. They have a very sophisticated ground game.
Romney was the frontrunner in Michigan and Ohio. The goal was to weaken him and give those states to Santorum. The fact there was such a strategy should tell reasonable people that when your enemy uses their vote to skew an election, it is not to improve your chance of winning in the general.
That being said, I will vote for anyone but Obama and Romney.