Undoubtedly, based on the actual facts, he accomplished much, including the gargantuan victory over the deficits, dysfunctionality in government, a broken health care system emergency.  Although there was an 85% Democratic legislature, he was able to work them to come to solutions that solved these key problems.

Notice how, until he started running for President, his approval ratings were high, considering it was a highly Democratic state.  His stance against gay marriage lowed his approval rating from 66% to 45%, but it came back to 56% before running for President.  But, as this is a positive indicator, I think the fact that he straightened out two huge problems (large budget deficit, healthcare program about to lose funding)  and did it working with Democrats mean he did what he promised by taking the job. 

Barbara Anderson, executive director of Massachusetts Citizens for Limited Taxation:

"I know you're busy with the Olympics right now," said the message she left on his answering machine, "but when you get back please save the commonwealth."

You may wish to see Video Documentary:  Mitt Romney - An Introduction (10:01) 

I've inserted here his statistics from  Governor Romney: The Before And After:

Context:  Romney made considerable progress against formidable and unusual odds in this state crisis!
              An 85% Democratic legislature, overrode 700 of his 800 vetoes.
              When Romney entered office in January 2003, Massachusetts was shedding jobs at a faster rate than the
                   country as a whole.  See How Bad It Was.
                   Massachusetts was one of the least attractive, due to its high cost of doing business and unfriendly
                       business climate.  Not a right to work state, high regulatory burden, high tax, Democratic control.
                       High cost of living. 

                                                                   BEFORE                       AFTER  

Budget                                                         Deficit $3 B                Surplus $1 B                                  !
                                                                                                      $2 B Rainy Day Fund                    !

Increase in median income                               $40,264                       $47,559          (18% rise)              !       

Companies considering Mass., sales force        13                               288                                           !

Unemployment                                                  5.6%                            4.7%
    Stopped highest job loss trend in the nation!                                                                                        !

Healthcare/insurance, no tax increase
    see discussion below                                   Broken                      Rescued                                       !

Streamlined state's permit process                   Byzantine                   Steamlined,                                  !
                                                                                                 "One stop shopping"
Massachusetts tax burden dropped
   National ranking                                             13th                           17th (that's positive)                     +

Massachusetts lost more jobs than
  anywhere else in the country,
  before Romney                                              50th                            36th (see citations)                      +
                                                                                                          12th his last year (BLS)

Trend in unemployment rate,                               50th                  In the top 10 in nation (positive)               !
                                                                                                       (7th most improved)

See for more detail on his actual accomplishments:  Economics And Jobs Record What He Actually Did


Of the things he had some control over or at least influence:  

      Took Mass. from $3B deficit to $1B surplus, plus a rainy day fund of $2B; worked with 85%
            Democratic Legislature to create solutions (Mitt Romney As Governor)
       Fees to direct users increased.  Romney used the principle of having users pay for their benefits from
           government organizations, such as licenses and other processing fees.  This raised $300 million.  Failing to
           see the logic, detractors accused him of raising taxes - wrong!  

       He also closed many tax loopholes, bringing in $181 million plus adding $128 million from taxing internet

       Implemented a New Market Tax Credit and extended the "Investment Tax Credit during 2003.  The
           unemployment rate dropped only from about

       Assure a windfall in capital gains tax revenue.

       Unemployment, considered not controllable over a short period, declined from 5.6% to 4.7%, which was a low
           rate of decline compared to other states. (And the politicians have said he wasn't a good governor based on
           one factor that is largely not controllable by a governor - plus the actual accomplishments were
           garguantuan!) - See Economic And Jobs Record, for actual facts of what he did. 

       Set up authorizations to catch up on school building projects.

       Added scholarship program and supported English immersion.

       Working with the state legislature, Romney developed the "Welcome Home Bill" which provides guardsmen
           with reduced life-insurance premiums and free tuition and fees at Massachusetts universities and
           community colleges; he increased their active-duty pay, plus a bonus on any guardsmen called to active
           duty in war zones; plus some tax exemptions.

       As governor, Romney signed off on a substantial increase in funding for the construction of thousands
           of new housing units, especially in urban or downtown areas.[51] A goal of this was to counteract the
           state's otherwise high housing prices.

       Laid ground work and incentives to improve the business climate in the largely business unfriendly state. 
           See Economic And Jobs Record.

       He did 800 vetoes, which were overridden by the Democratic legislature.

He had high approval ratings (until he started running for President, when Democratic support plummeted in this Democratic state.  His many days outside of the state led to disapproval. 
The courts ruled that gay marriage would be legal and that the state health program had to pay for abortions, so he had no control in regard to those.

In May 2005, Romney presented a proposal to the Massachusetts General Court to crack down on repeat drunk drivers. Massachusetts had some of the weakest drunk driving laws of any state in the country, and the state was losing $9 million annually from its highway budget because existing laws were not in compliance with federal standards


He was told at the beginning of his governorship that the best way he could help people would be to assure they had medical coverage. 

Romney gathered experts together to create an innovative solution (Obama went to those same experts for their expertise).   He designed something that was specific and only workable in his own state.
This was the first of its kind in the nation:   

Romney decided that because people without insurance still received expensive health care, the money spent by the state for such care could be better used to subsidize insurance for the poor   After positing that any measure adopted not raise taxes and not resemble the previous decade's failed "Hillarycare" proposal, Romney formed a team of consultants from different political backgrounds that beginning in late 2004 came up with a set of innovative proposals more ambitious than an incremental one from the Massachusetts Senate and more acceptable to him than one from the Massachusetts House of Representatives that incorporated a new payroll tax. 

He determined the best road to success for his state would be via an individual mandate, which is really at its core only a charge for free riders, who could afford insurance but chose to mooch off of the state for free care in the emergency rooms - they weren't mandated to have insurance, but instead to pay for the availability of the care they did receive.  Together with the support of Ted Kennedy, the effort eventually gained the support of all major stakeholders within the state, and Romney helped break a logjam between rival Democratic leaders in the legislature. 

He means-tested state subsidies for people who do not have adequate employer insurance and who make below an income threshold, by using funds previously designated to compensate for the health costs of the uninsured

The state legislature added a few things later, which he vetoed, but he was overriden by the Democratic majority legislature.   Romney points out that there was no government takeover and that he kept the insurance private.  

He staged well-organized media events to appeal directly to the public rather than pushing his proposals in behind-doors sessions with the state legislature.

Although attacked by Republicans after ObamaCare borrowed some concepts, the plan was lauded by conservatives as an innovative model using conservative principles:   free market, no new taxes, and insurance exchanges - all private.   He vetoed the addition of the legislature of a charge (fairly modest) to employers, but it was overriden.  The charge to the free riders was a principle derived from the original proposals by the conservative Heritage Foundation, one which he always favored:  that people fairly pay for the services they use (called user fees, not taxes).  Read more on this in the Contents/Links Romney directory or RomneyCare Is A Great Conservative Accomplishment.  


Romney was especially effective in dealing with a crisis of confidence in Boston's Big Dig project following a fatal ceiling collapse in 2006, wresting control of the project from the Massachusetts Turnpike Authority and helping ensure that it would eventually complete.  (He had attempted to change management before that but the politicians blocked it.  He finally got rid of the major culprit, who also went to jail.)


Despite his highly favorable rating, he projected that the upcoming elections would be very difficult for Republicans.  Meanwhile he was promoted by others as a possible candidate for President.  He decided, I think rightly, that he would go for the Presidency. 


He was also elected Chair of the Republican Governors Association,

Schools have scored first in national math and science tests and Romney held out until the Legislature gave him a tough new drunken driving law he demanded."

See Wikipedia, Governor Of Massachusetts 

Overview and links
Contents/Links Romney

Governor Romney:
The Before And After - Excellent job!


Mitt Romney - An Introduction (10:01)

For more depth: