In Mr. Sanders, she faces an opponent who has already competed statewide in Massachusetts, in 2016, when he lost narrowly to Hillary Clinton.
Mr. Sanders won 48.7 percent of the vote in that race and was strongest in the more working-class areas of western Massachusetts, carrying more than 70 percent in some precincts that bordered his home state of Vermont.
Mrs. Clinton’s entire margin of victory — which was a little more than 17,000 votes — was from Boston, where she outpaced Mr. Sanders by nearly 20,000 votes.
Mr. Sanders has another advantage: He has run more than $3.4 million in television ads in the Massachusetts markets, mostly in Boston; much of it came in advance of the New Hampshire primary in an attempt to reach voters in the southern part of that state. Ms. Warren has run about one-fifth as many ads: $700,000 worth and none since the New Hampshire primary.
In recent weeks, Mr. Sanders has spent about $400,000 on television ads in Boston, Springfield and Providence, R.I.
On Thursday, Sanders volunteers began organizing a four-day “Berniepalooza” in Worcester, Mass., complete with musical acts and door-knocking across the state. “Canvass all day, party all night, and repeat,” says the event invitation on Facebook.
What the Sanders campaign does not have in Massachusetts is a formal state director, after Joe Caiazzo, who was moved to Massachusetts from New Hampshire, left at the end of last year. Shannon Jackson, who oversaw the Sanders victory in New Hampshire, is now in charge of the northeastern region of the country. The campaign moved New Hampshire staffers over to Massachusetts after that primary.