BOSTON — As Bernie Sanders prepared to rally thousands just down the road, Elizabeth Warren’s campaign co-chair made a plea to her nervous supporters.

“They are trying to erase her,” Rep. Ayanna Pressley (D-Mass.) warned a crowd of volunteers packed into a sweaty field office a mile from Fenway Park. “Don’t you dare ride the poll-er coaster.”

But some of the Massachusetts senator’s most ardent supporters fear that ride is about to end.

Warren has spent the past days chasing frantically across the country in a desperate search for Super Tuesday delegates. But her biggest problem might be back at home. Warren faces the real risk of losing Massachusetts to Sanders, a blow that could knock her out of the race. And as Warren raced from South Carolina to Alabama to Texas, Sanders dropped into her home state this weekend to try to seal her fate.

“On Tuesday, if we have the largest voter turnout in the history of the Massachusetts primary, we can win here in Massachusetts,” Sanders said in Boston.

Three separate polls released in recent days show he’s right. Sanders, from neighboring Vermont, has inched ahead of Warren in her home state, buoyed by his strong showing in the early states and Warren’s failure to finish higher than third place in any of them.

A home-state loss would be devastating to Warren. It’s hard to see how she would continue after Super Tuesday at that point, especially since Massachusetts shapes up as by far her best chance of winning a Super Tuesday state.

While other candidates exiting the race likely benefit Joe Biden more, Bernie Sanders’ team thinks Warren dropping out would help him further consolidate the progressive vote.

“If Elizabeth wasn’t in the race, the main beneficiary, without question, would be Bernie.”

“If Elizabeth wasn’t in the race, the main beneficiary, without question, would be Bernie,” said Rep. Mark Pocan (D-Wis.), the co-chair of the House Progressive Caucus and a Sanders supporter.

And while Warren is signaling she’s in it for the long run, Pete Buttigieg’s sudden decision to drop out Sunday shows that candidates are often all-in — until they’re out.

Warren repeatedly dodged when asked this past week if she’d win there, a telling sign.

"I know that Massachusetts is a very progressive state and progressive ideas are very popular. And so I'm sure that's why Bernie is campaigning there,” she told reporters in South Carolina Saturday.

Sanders has spent heavily on ads in Massachusetts, which borders is home state and he nearly won in 2016. Warren has barely spent any money on the state — but in a sign they’re concerned Massachusetts might slip away, a new super PAC backing Warren announced Thursday night that they’d include the Boston media market in a last-minute, $12 million ad buy.

A number of volunteers at Warren’s canvassing kickoff event in Boston Saturday told VICE News said they feared she’d have another rough election night on Super Tuesday. They expressed frustration that more voters hadn’t bought into her vision. And as Sanders swung through the state for a pair of rallies, some openly fretted that she might lose Massachusetts and be forced from the race.

“There are a whole lot of people who are voting based on who has already won. I still love Warren and deeply want her chances, which are not as great, to pan out. And I'm more angry about sexism,” said Ilana Gelfman, an attorney who’d come out to knock doors for Warren.

“I don't want it to end on Tuesday,” said Eli Sprecher, a pediatrician.

They’re not alone in their assessment — or frustrations.

“This is a critical time. Super Tuesday will narrow the field,” Rep. Jan Schakowsky (D-Ill.), who endorsed Warren early on, told VICE News on Thursday. “I’m hoping she’s still there.”

As Warren’s surrogates rallied what the campaign said was 200 people Saturday morning, Sanders was a few miles away on Boston Common, revving up a crowd his campaign claimed topped 13,000 people. The night before in Springfield, out in western Massachusetts, he’d drawn almost 5,000 people. Warren could draw crowds that big early in her campaign, but it’s been a while since she’s done so.

Sanders supporters were mixed in their views of Warren — some attendees at his two rallies praised her while others heaped scorn on their home-state senator.

Kyle Murphy, a public policy analyst who’d come to see Sanders in Boston, said he’d gone back and forth between the two candidates up until “when I was voting” early last week, and still felt “a bit conflicted” about his vote for Sanders. He liked how detailed Warren’s policies were and thought she had a better chance of uniting the party. But: “I like the outsider.”

But Danielle Lupus, a chef from suburban Boston who was leaning towards Sanders over Amy Klobuchar. She didn’t like Warren because she was “too mouthy” and “has the same plan that Bernie has but puts Bernie down.”

Warren’s campaign argues she’s resurgent. She saw a huge fundraising surge in February, raising $29 million in the month, including almost $10 million in just the three days after her stellar Nevada debate performance. Warren campaign manager Roger Lau released a memo Sunday looking to calm worrying supporters that said the campaign has already put $4.1 million towards ad reservations in states that will vote after Super Tuesday, a signal she’s not going anywhere.

“We believe that Super Tuesday will greatly winnow this field and it will become clear that only a few candidates will have a viable path to the Democratic nomination — and Elizabeth Warren will be one of them,” he wrote.

Sanders never mentioned Warren in his Massachusetts rallies, though he did take swipes at the super PACs in the race — a veiled shot at her recent reversal to accept super PAC support. And a surrogate trolled Warren during his Springfield rally, by adopting her rhetoric to talk about Sanders.

“I am ready for a new president who believes in big, bold, structural change, and who has the courage, the passion and the plans to make it happen,” Massachusetts state Rep. Lindsay Sabadosa (D) said as she introduced Sanders.

Warren’s team likely wouldn’t love that dig. But they’ll like it even less if she loses her home state Tuesday and gets pushed from the race.