The margins are close, but if you dig deeper into the DMR data, you’ll see that Warren may be in even better shape than those top-line numbers indicate. That’s because the Iowa caucuses aren’t one big election; they’re actually 1,679 smaller elections, one in each precinct. And there’s a twist: Whenever a candidate doesn’t reach the state’s 15 percent “viability threshold” in the first round of balloting in a particular precinct, their supporters have to disband and “realign” with another candidate (or go home). If the Register’s numbers are right, only Sanders, Warren, Buttigieg and Biden would currently meet the threshold statewide; the other 19 percent of likely caucus-goers who preferred a lower-polling candidate would have to realign in the room.

That means second choices are crucial. And guess who’s currently Iowa’s top second-choice pick, according to the Register poll? Warren. Her 16 percent on that measure edges out Buttigieg (15 percent), Biden (12 percent) and, most importantly, Sanders (12 percent), giving her the highest combined first-and-second-choice score in the field (33 percent). Warren’s net favorability rating (+46 percent) is also higher than Buttigieg’s (+44 percent), Sanders’s (+37 percent) and Biden’s (+29 percent). It’s quite possible, then, to imagine a scenario in which Sanders leads on the first ballot and Warren overtakes him after realignment. In fact, the Register’s pollsters have already calculated that Warren would gain a point if Cory Booker’s supporters were reallocated after his decision Monday to drop out — and Sanders wouldn’t gain at all.