Massachusetts Attorney General Martha Coakley won the Democratic primary for governor Tuesday night, narrowly beating her closest rival, Steve Grossman, setting up a showdown with Republican nominee Charlie Baker and three independents in November.

Supporters roared in the gilded ballroom of the Fairmont Copley Plaza as Coakley took the stage to deliver her acceptance speech.

"Tonight, you have sent a powerful message,” Coakley said to the crowd. “The insiders, the big money Super PACs wont be deciding this election. It will be decided by fair, hardworking men, women and children who just want a fair shot.”

Coakley sounded populist themes in her acceptance speech and she previewed the next 56 days of attacks on Charlie Baker, a former health insurance executive and two-time candidate for governor.

"Charlie Baker believes voters won't remember he ran as a Tea-Party conservative in 2010, railing against what he called the bathroom bill and putting Gov. Patrick's face on EBT cards as a political stunt," Coakley said. "Voters are smart enough to see through Charlie's superficial transformation."

Coakley’s victory was not unexpected: Polls predicted she would win by anywhere from 12 to 20 percentage points. Instead, she won by only six.

This relatively slim margin might worry some Democratic voters who are still smarting from Coakley’s devastating loss to Scott Brown in the special election for U.S. Senate in 2010. But this past year, Coakley has tried to shed her earlier image as aloof and overconfident.

“I said when we started this campaign that no one would work harder, knock on more doors, make more calls, and shake more hands than we would, and thats exactly what we did,” Coakley said. "We ran, we fought and we stood for something that matters.”

Down the street, state Treasurer Steve Grossman addressed his supporters at the Park Plaza Hotel. He said his campaign came close, but that he had called Coakley to congratulate her.

“I told Martha Coakley I will do everything I can, and I hope all of you will do everything you can, to make sure Martha Coakley becomes the next governor of Massachusetts,” Grossman said to his supporters.

And Don Berwick, who ran to the left of Grossman and Coakley for the democratic nomination, thanked his supporters for their work and sacrifice. In a statement, the former federal healthcare administrator said that they united around a mission to make the commonwealth a better place. And that mission continues.

Berwick and Grossman will attend a unity breakfast Wednesday morning to pledge their support to Coakley, but how long will it take for their foot soldiers to do the same? Coakley, no doubt, is hoping it's before the November 4 general election