With just two days before 2 million or so Florida Republicans vote in the first large-state primary, the latest NBC/Marist poll announced today shows Mitt Romney opening up a sizable fifteen-point lead over Newt Gingrich. (Nate Silver now puts Romney’s probability of victory at 95 percent.) Just 4 percent of likely voters claim to be undecided, which makes a last-minute shift like the one we saw in South Carolina a virtual impossibility — not that anything’s ever truly impossible in this race.