“If Bernie wins those first two states, I think the establishment will have a collective freakout the likes of which we have never seen before,” Rebecca Katz, a progressive Democratic strategist, said. “We’re in for a very long and hard fight with lots of ugly attacks and big money spent.”

Gaming out a scenario where Sanders wins Iowa, more than a half-dozen Democratic operatives, pollsters, and activists interviewed acknowledged the possibility that a New Hampshire victory could likely follow, turning voters’ attention to the Nevada caucus, which was viewed as a critical turnaround moment in Clinton’s campaign.

“It’s hard to argue that it doesn’t change the calculus,” one progressive strategist familiar with Sanders’ 2016 early state operation said, arguing that if Sanders wins the first three contests, including Nevada—a possibility multiple Democrats privately acknowledged, with various degrees of confidence and skepticism—it could have a catalytic effect on the rest of the primary.

“If that happens there’s no stopping him,” the strategist said.