In the heart of Cambridge, 2 miles from where Senator Elizabeth Warren lives and just blocks from the campus where she used to teach, an idyllic day was unfolding for the Warren campaign. A crowd of around 50 supporters lifted signs bearing her name outside of a local coffee shop, chanting “I am a Warren Democrat!’’ as passing drivers honked their encouragement. Early voting had begun on the senator’s home turf, and even the elusive Massachusetts sun was cooperating, sparkling brightly in the middle of February.

“We are in Cambridge, the bluest city in the bluest state and home of the next president of the United States, Elizabeth Warren,’’ Marc McGovern, a city councilor and former mayor of Cambridge, shouted to a cheering crowd.

Then the bubble popped.

“Give it up! She’s gonna lose!’’ shouted a heckler as he hustled past the enthusiastic crowd. “Ber-nie! Ber-nie!’’

Warren’s supporters clapped and cheered, drowning out the naysayer with their enthusiasm — but still.

With a week to go before Super Tuesday, Massachusetts is now witnessing an all-out war between Senator Bernie Sanders and Warren, two progressive stars hoping to notch a victory in a reliably progressive state. And Warren is facing a home-state paradox here: Candidates don’t get much credit for winning their home states but can be eviscerated for losing them.

“It matters to the Warren campaign more than the Sanders campaign,’’ said Shannon Jenkins, a professor of political science at the University of Massachusetts Dartmouth. “If Elizabeth Warren can’t win her home state, that’s a real blow to her campaign. If she does win her home state, and Sanders loses, then Sanders can say, well it’s her state. Of course we expected her to win that state.’’

It looks like it will be a strikingly close contest, with a recent poll from the University of Massachusetts Lowell suggesting that the two candidates are running neck-and-neck for first place. Sanders was at 21 percent among likely Democratic voters and Warren was at 20 percent, with a margin of error of 6.1 percent. (The poll took place before Warren’s widely praised performance in the Nevada debate).

Because of that, both campaigns are pouring energy into a primary that doesn’t usually get much attention. (Thirteen other states will also hold nominating contests on March 3). On Monday, the Sanders campaign rolled out 18 new Massachusetts endorsements, most of them current and former city councilors or state legislators. The campaign also said that volunteers had knocked more than 50,000 doors over the weekend and is planning a rally with Sanders in Springfield Friday evening. In Worcester, there will be a four-day “festival of music and door-knocking’’ called “Berniepalooza.’’

“Our momentum in the Bay State only continues to grow,’’ said Trip Yang, the Sanders statewide political director, in a statement.

The Warren campaign said it had knocked on over 57,000 doors in the last two weeks and held more than 100 events across the state over the weekend. Many of the most prominent members of the Massachusetts delegation have thrown their support behind Warren, including Representative Ayanna Pressley (who broke with the rest of the so-called “squad’’ to support her), Attorney General Maura Healey, Senator Ed Markey, and Representative Joe Kennedy, who greeted the crowd outside of the Cambridge coffee shop on Monday. State Senate President Karen Spilka has also endorsed Warren, and on Monday, House Speaker Robert DeLeo did too.

“Elizabeth Warren has built a statewide grassroots organization in Massachusetts starting in 2012, which defeated a popular Republican incumbent. Today that organization has expanded to include thousands of first-time volunteers, small donors, and students,’’ said Jossie Valentin, Warren’s statewide director.

But Sanders has now won all three nominating contests so far, which may put Warren in jeopardy, even close to home.

In the 2016 primary, Sanders lost the state to Hillary Clinton but won areas outside of Greater Boston, notching victories in Western Massachusetts and the Cape and Islands. This year, Warren and Sanders are battling over the territory that Sanders carried then, and voters seem legitimately torn. Some houses in Northampton display both Sanders and Warren yard signs side by side.

At Smith College on Monday, Ben Cohen and Jerry Greenfield of Ben & Jerry’s ice cream hosted a Sanders ice cream social, doling out scoops and encouraging college students to canvass their friends.

“There’s never been a candidate like Bernie,’’ Greenfield said.

The Sanders campaign hired a field director in Massachusetts last month and has four offices in the state, including one that just opened in Holyoke. On Monday afternoon, a half dozen volunteers set up that office in a rented garage. A huge banner read “In Poll after Poll after Poll, Bernie Beats Trump,’’ which has become a catchphrase of the campaign.

The Warren campaign has two field offices — in Cambridge and in Northampton — and has had staff here for a year.

But with Democrats desperate to beat President Trump and frantically analyzing their options, even some Warren loyalists might be second-guessing themselves as they see Sanders gaining ground nationwide, said Erin O’Brien, an associate professor of political science at UMass Boston.

“In a pure preference poll, Elizabeth Warren crushes in Massachusetts,’’ O’Brien said. “But with Donald Trump in the White House, and her underperforming in the early races, some Democrats are leaving her — not because they want to, but because they think [Sanders] has more of a shot,’’ because of his wins so far.

Still, the home state advantage might win the day. Warren’s supporters say they have longstanding relationships with her, extending back years. At a campaign event in Cambridge on Sunday, Deborah Downes, whose son Patrick lost a leg in the Boston Marathon bombing nearly seven years ago, spoke in support of Warren, saying that the senator had stuck by the family ever since. A year after the bombing, Downes sat at the Marathon finish line, weeping as she and her husband waited for their son to finish the race on a hand cycle.

“We sat in the stands, we were by ourselves — no one knew who we were — and she came bounding up the steps . . . sat down between us and held my hand,’’ Downes, 67, said in an interview as volunteers set off to knock on doors. “I’ll never forget that.’’

Globe correspondents Lucas Phillips and Laurie Loisel contributed to this report. Zoe Greenberg can be reached at zoe.greenberg@globe.com.Follow her on Twitter @zoegberg.