With a week to go until the Iowa Caucuses, it may all hinge on which candidate has the best ground game. This episode, political correspondent Mara Liasson and campaign reporter Scott Detrow join host Tamara Keith. Find them on Twitter @MaraLiasson, @scottdetrow, and @tamarakeithNPR, or at npr.org/politics — or email the show at nprpolitics@npr.org.