Monday night’s sedate Democratic gubernatorial debate at the Kennedy Library may not have made reporters happy, but it should embolden those who hope to expel the Republicans from the State House’s corner office in November.

The absence of fireworks among Treasurer Shannon O’Brien, Senate president Tom Birmingham, former secretary of labor Robert Reich, businessman and former Democratic National Committee chair Steve Grossman, and former Watertown state senator Warren Tolman means that Democratic leaders will have less damage to repair when one of the five meets Romney in November. While it’s unlikely that the equanimity among the bunch will last, the big story of the debate was the extent to which the candidates agree on many of the issues.

Ideologically, differences among them are scant. O’Brien and Grossman lean to the right on fiscal issues; Reich and Birmingham lean more to the left. Tolman is a solid Clean Elections candidate. But aside from that, their differences are more personal than ideological. All five favor legalizing medical use of marijuana to treat some illnesses. All five are strongly pro-choice, including O’Brien, who, after a flirtation with a more socially conservative position early in her career, now brandishes the "woman’s right to choose" banner.

Most important, any of the five could win greater labor support than Attorney General Scott Harshbarger received during his 1998 run. (Back then, Governor Paul Cellucci, with his homegrown Italian-American roots and express overtures to labor as a legislator, attracted some overt labor support while convincing others in the ranks to avoid Harshbarger.) All five candidates schmoozed at a state AFL-CIO meet-and-greet held at the Kennedy Library Tuesday night, at which Romney was notably absent. And let's not forget that labor attacked putative Republican gubernatorial nominee Mitt Romney once before in a Massachusetts political race, during his 1994 bid for Senate against Ted Kennedy.

That said, in Monday’s debate neither Reich nor O’Brien, the two frontrunners, performed as well as he or she has in the past. Reich wisely mentioned his management of the multi-billion-dollar US Department of Labor, but missed a chance to stress that he is the only Democratic candidate without State House encumbrances. O’Brien failed to trumpet her role in blowing the whistle on the Big Dig when asked by the Boston Globe’s Joan Vennochi if she were too much of an insider to tackle state problems. On the other hand, Tolman deftly exploited a chance to criticize the state legislature for rushing through the exorbitant subsidy package for the Boston Red Sox. Birmingham, for the first time, appeared relaxed and in Happy Warrior mode — reminiscent of Hubert Humphrey in 1968. And Grossman showed steady progress in conveying that he possesses the requisite management skill to steer the state in the right direction.

Romney strategist Mike Murphy crashed the night’s festivities, taking the opportunity to criticize all the Democrats collectively. "Mitt Romney won the debate," Murphy told TV reporters afterward.

It is certain that Murphy will try to paint all the Democrats as too liberal to run the state. But with Tuesday’s news that former Melrose mayor Patrick Guerriero was dropping out of the race for lieutenant governor, Murphy may have to revise his strategy. If the eventual Democratic nominee can demonstrate that Romney is too conservative on social issues — as evidenced by his quick dismissal of the openly gay Guerriero — some independents may find themselves rushing back to the Democrats.