Democratic presidential insurgent Bernie Sanders is planning a major offensive in one of Hillary Clinton’s favorite haunts — Massachusetts — in a bold move to shock his rival in a potentially crucial faceoff, a top Sanders strategist told the Herald.

“I think Massachusetts could be a really pivotal, important battleground this year,” Sanders campaign senior adviser Tad Devine said in an interview. “We’re going to try to put together a real organization there.”

A Sanders upset in the Massachusetts primary, scheduled for March 1, would be a major blow to Clinton, whose support is so strong here that the late Ted Kennedy dubbed it “Clinton Country” during Bill Clinton’s presidential campaign.

Hillary Clinton got a major boost in 2008 when she trounced Barack Obama in Massachusetts’ presidential primary, despite Obama’s strong start in early primary states.

But Devine, a former top strategist for Kennedy and former Massachusetts U.S. Sen. John Kerry’s 2004 presidential campaign, said the self-described socialist Vermont senator plans to hire staff soon and launch a grass-roots campaign because of the state’s liberal electorate and potential importance in the 2016 primary schedule.

“Our focus is going to be on the early states,” he said.

The state also could have added juice because of home state U.S. Sen. Elizabeth Warren, a liberal darling whose decision to take a pass on 2016 helped Sanders gain a foothold. Warren has so far kept her distance from Clinton, even heaping praise on Sanders last weekend in a widely read interview with the Herald.

A Warren endorsement — either for Clinton or Sanders — could be a major factor in who grabs the state’s 121 Democratic delegates, a substantial haul in a tight primary race.

Devine said Massachusetts could have a “major impact” on who gets the Democratic nomination.

The Bay State has always been a poor cousin in the presidential primary process, but that is expected to change next year, with a possible Clinton-Sanders matchup and a crowded Republican field. The March 1 primary is part of a 12-state Super Tuesday contest.

Though Clinton has also enjoyed strong support in Massachusetts, especially in fundraising, the state has been receptive to insurgent liberal underdogs like former Gov. Deval Patrick.

But Sanders’ surprising emergence as a Democratic rock star could make Clinton’s campaign nervous even in states like Massachusetts that were considered slam dunks.

In the Herald interview, Devine also said he expects the Clinton-affiliated super PACs and other rivals to launch attacks soon on Sanders’ record and electability. But he ruled out running any negative attack ads against Clinton and said Sanders’ strong early start shows that his grass-roots approach is working.

“We wanted to get him positioned as a serious, credible candidate and I think we’ve done that,” Devine said.

Asked about Sanders’ plans to handle negative ads, the senior strategist said, “That’s something we’ll have to deal with … we’re going to see people who are part of (Clinton’s) campaign making attacks against him. We can’t get distracted by it.”