Capuano had been considering the race for some time. Recent polling showed him taking 21 percent of the vote to Attorney General Martha Coakley's 41 percent support, if he had chosen to run. 

Capuano had previously challenged Coakley, who recently announced her intentions to run in the gubernatorial race, in the 2010 special Senate election. She defeated him in the Democratic primary but later went on to lose to former Sen. Scott Brown (R) in a devastating defeat for Democrats.

Though she received criticism for blunders on the campaign trail and in the management of her team during that race, she enters the current gubernatorial race the Democratic front-runner.