He’s up in three of the four latest Iowa polls, including an Emerson poll that is the best for him so far in Iowa, showing him leading Biden by 9 and, crucially, Warren at 11 percent, beneath the threshold for viability (although she’d be viable in her stronger precincts). In New Hampshire, he’s led in all the recent polls. Nationally, he’s a step behind Biden in almost all the surveys, but the two have separated from the rest of the field.

The result in Iowa next week could make the difference between Biden taking control of the race, or Bernie starting a roll that it will be painful and divisive for Democrats to stop, assuming that they can.