Pretty sure it's this one, based on the hair.
http://store.americangirl.com/agshop/static/kitdoll.jsf/title/Kit+%26+Ruthie/saleGroupId/300/uniqueId/59/nodeId/11/webMenuId/5/LeftMenu/TRUEThey're spendy and there's quite the cottage industry in making matching clothes for the doll and girl (or selling patterns for relatives who know how to sew to do- I'm going to go out on a limb and guess this is one of those because I like to think a professional wouldn't use that fabric in a non-pajama application.) For some reason conservative homeschoolers tended to be pretty fond of them- I'm guessing because of the "wholesome values" thing and because they do get a little history into a kid in a painless way- there are books to go with each doll and each one represents a different subculture and time period in American history. Within the past few years they've fallen out of favor with the fundie set because the books are sorta feminist and the parent company is apparently outspokenly so. I'm pretty sure some fundie website played Six Degrees of Kevin Bacon and connected them to some charity to some other charity and from there to Planned Parenthood as well, and of course that's the kiss of death in that crowd.
The girl in question looks a bit old to be carrying a doll around (though about the prime age for the dolls in question- they're really more for collecting and accessorizing a la Barbie than getting down on the floor and playing with) and sobbing in public, but if the doll is a special favorite of hers wearing the matching outfit and carrying it on a day where there would be a lot of family stress and probably not a lot of attention doesn't really seem all that odd, other than being a touch infantile for her age.
That said, my main concern is that Santorum felt the need to drag his crying kids out in public for some reason. Politics completely aside, when those kids get older and realize that could have been avoided I'm betting one of them will punch him in the snoot for it. My money's on the kid who looks like a chubbier, startled Harry Potter.