The time and hassle obstacles pretty much guarantee that the likely fill-in candidate would be GOP VP contender Mike Pence. Now the RNC voters don’t have to choose him just because he is the VP candidate, but the time factor, the fact that he got generally high marks for his one debate joust with Democratic VP contender Tim Kaine, and the fact that he’s a GOP party insider, make him a near shoo-in for the fill-in spot.