Chuck Todd, NBC News has the latest details on the Iowa shake-up of the GOP field, and discussing the differences between the candidates, with Jen Psaki, fmr. White House deputy comm. dir.; Phil Musser, fmr. Romney 2008 campaign advisor; and Sara Fagen, DDC Advocacy partner. Also, Robert Costa, National Review reports on Rick Santorum's chances against Mitt Romney, going into New Hampshire.