A number of questions came up over the weekend about just what the credentials committee is and how its membership is choosing. Usually it's a meaningless rubber stamp, like almost all modern party conventions. But this year, that's the committee that will have the final say on which state delegations get seated. So if we're still arguing about the non-sanctioned Florida and Michigan primaries in August, the credentials committees is the group that gets to make the final determination. Greg Sargent explains just how it works.