Iowa is key for every 2020 contender. For Bernie Sanders, it might be everything.

For weeks, a polling famine has left few clues into who could capture enough fire to win the Iowa caucus. One highly anticipated survey released on Sunday served pundits a cold political buzzkill—showing a three-way tie between Sanders, former Vice President Joe Biden, and former South Bend Mayor Pete Buttigeg—and providing an opaque glimpse into the unknown status of the February’s inaugural event. The high production value Democratic debates, set to descend on Des Moines next Tuesday, have done little to tip the scales either: the same leading trio have qualified to compete on stage for the seventh time, as they have during each prior televised event.

But as Feb. 3 nears, some Democratic strategists, pollsters, and activists at the national and early state levels are giving a cautious nod to the notion that if Sanders competes strongly enough to win the Hawkeye State, he could activate an avalanche of successes that would significantly complicate the path forward for the rest of 2020’s top tier.

“For everybody else in the field, it’s a problem if Sanders wins the first two,” Jeff Link, a longtime Democratic pollster in Iowa, told The Daily Beast. “He’s going to have a head of steam going into Nevada and South Carolina and Super Tuesday.”

Sanders’ campaign has gone to great lengths to ensure that happens, launching a do-or-die offensive focused on locking down the state he narrowly lost as an insurgent alternative to Hillary Clinton in 2016. Now, for the first time in the cycle, he leads polling averages, showing an upward trajectory over the past several months. In nearly a dozen Iowa surveys released since mid-October, when Sanders re-emerged more energized after suffering a heart attack, he has remained firmly in place, or, at times, risen in standing.

“Bernie Sanders is enormously underrated in this race,” Peter Leo, chairman of Iowa’s Carroll County Democratic Party, said. “He’s come back stronger than ever. I’ve even noticed the amount of energy the man has post-surgery.”

Looking to capitalize on that momentum, the Vermont Independent has taken care to distance himself from his top rivals, escalating in rhetoric and campaign materials with just weeks until voting commences. In an interview with CNN on Monday night, Sanders sought to contrast his record with Biden’s on issues of particular significance to Midwestern voters. His critique of the North American Free Trade Agreement, one of his campaign’s signature attacks, argues it cost American workers “millions of jobs.” On Tuesday morning, he published an op-ed in the Des Moines Register, the influential paper whose endorsement several presidential aspirants are courting, seeking to draw sharper distinctions with his rivals on health care and other progressive issues.

“Unlike some of our opponents, we are not proposing to appease pharmaceutical companies and the health insurance industry that are bankrupting over 500,000 people every year and denying Americans adequate medical treatment—we are going to end their profiteering once and for all,” he wrote.

In the latest CBS/YouGov poll, Sanders is tied with Biden and Buttigieg at 23 percent, with each hypothetically securing a similar number of delegates out of the caucuses, the survey indicates.

That is to say, Sanders’ status as a frontrunner remains viable, but tenuous. While he enjoys the enthusiastic energy of a massive volunteer base of grassroots supporters, and the highest fundraising haul of any contender to date, totalling $34.5 million in the fourth quarter, he’s within striking distance of Buttigieg and Biden in multiple matchups, with some Democrats on the ground scratching their heads about who might have an edge, and wondering where Sanders fits into the mix.

“No one is really showing their volunteer armies yet,” Sean Bagniewski, chairman of the Polk County Democrats in Des Moines, said. “It might shock the hell out of us.”

Following just seven days after Iowa, in New Hampshire, where Sanders swept in 2016 by double-digits, he has a home-away-from-home edge. Having traveled to the state during the 2018 midterm elections (some operatives quipped he never really stopped campaigning after 2016), Democrats in the Granite State recognize Sanders as a familiar and formidable force. Sen. Elizabeth Warren (D-MA), who also enjoys a possible neighboring state advantage, has slipped in recent surveys, falling to a distant fourth place from Sanders’ first.

“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.

Nevada hasn’t seen a poll since mid-November. Two surveys released that month place Sanders and Warren in a statistical tie, well behind Biden in the top slot. In aggregate averages, the former VP dominates by 10 points. But Sanders has recently gained traction with Hispanic voters, a critical base of supporters in Nevada courted by multiple candidates that the senator has also targeted through much of his 11-month campaign.

In the latest Fox News poll, Biden leads Sanders by 6 percentage points overall. But 31 percent of Hispanic voters are backing Sanders over Biden, who earns 24 percent.

“Bernie’s ground game in Nevada is off the hook,” a separate unattached Democratic strategist said.

That echoes Sanders’ national uptick with Hispanic voters, following his endorsement from Rep. Alexandria Ocasio-Cortez (D-NY) in October. Sanders now has a 12-point lead over Biden with Hispanic voters nationally, capturing more than a third of that voting bloc, according to a recent Morning Consult poll.

All of that legwork leads to South Carolina, the first-in-the-South primary conventionally expected to serve as a firewall for Biden, who enjoys overwhelming support from African American voters in the state. The former vice president is a favorite to win the primary, with multiple sources pointing to his consistent support from one of the Democratic Party’s most loyal constituencies. The stars would have to align perfectly for all of that to change—that is, for Biden’s support with black voters to evaporate—and for Sanders to be the heir apparent to that collapse.

Anything is possible, strategists and party officials say, but it would be a tall order.

“I think there’s a lot of fluidity here,” Carol Fowler, the former South Carolina Democratic Party Chair, said. “But I don’t think it’s going to be as determined by Iowa’s outcome as it was in 2008.”

In the lead-up to the 2008 primary, the smart money was on Hillary all the way. Then, when little-known freshman senator Barack Obama won the Iowa caucus, the electoral calculus realigned in his favor, with a significant population of voters in South Carolina voting to elect the first black president.

Fowler cautions it’s trickier this time to imagine such an outcome boosting Sanders.

“While of course Bernie has some support, I don’t see his support growing all that much because of what happens in Iowa and New Hampshire.”

In 2016, when Clinton was up again after competing eight years prior in the state, she overperformed expectations, handily creaming Sanders, a defeat his team has taken steps to avoid repeating in 2020. Since the launch of his campaign in March, Sanders has traveled to South Carolina multiple times, picking up a variety of endorsements from local elected officials, including a mayor who formerly backed Sen. Kamala Harris (D-CA), who dropped out in December.

His efforts have caused other party officials to take note. “I have been very interested and somewhat impressed to see that Bernie Sanders appears to have learned from the mistakes Bernie Sanders made in 2016,” Trav Robertson, the South Carolina Democratic Party chairman, told The Daily Beast. “He’s not campaigning at the African-American community, he’s campaigning in the African-American community.”

Antjuan Seawright, a South Carolina-based Democratic strategist, included Biden alongside Sanders in his calculation. “If Bernie is the winner of Iowa and New Hampshire and Biden wins Nevada and South Carolina, I think they’re both well positioned to compete in Super Tuesday,” Seawright said. “Bernie’s fundraising haul gives him the ability to compete in multiple places.”

While polling shows an overwhelming South Carolina lead for Biden—coming in at 35 percent in averages to Sanders’ 15.3 percent—some surveys suggest that gap may be narrowing. Asked for comment about state strategy, a Sanders campaign official pointed a Post and Courier/Change Research poll, the most recent data available in the state, which shows Sanders gaining the most ground of any candidate in South Carolina. In that survey, the Vermont senator is within 7 points of Biden.

In addition, a separate poll offers another way for Sanders to crack Biden’s firewall: as a default pick. A Quinnipiac University survey from November shows that 17 percent of Biden supporters list Sanders as their second choice favorite, the most of any candidate. Multiple strategists acknowledge that if Biden underperforms expectations in the early contests leading up to the Palmetto State primary, that #2 option becomes more relevant.

“It is absolutely irrational to deny momentum,” Robertson said. “I do think Bernie Sanders has learned from his campaign in 2016, and I’ve seen it.”