As Democrats converge in Boston this week, the Republican governor of Massachusetts, Mitt Romney, is riding high.

He has been heralded by Bostonians and local scribes alike for breaking the two-year impasse between the city and its police unions just in time to prevent mass picketing and protests outside of the Fleet Center during convention week.

He is considered one of the rising stars in the national Republican Party. And he is smack in the middle of the controversy over who should replace Sen. John Kerry (D-Mass.), should Kerry be elected president this November.

So how do the Democrats, who panicked over the possibility of infuriating their union backers by crossing picket lines or watching their convention devolve into a series of canceled events, thank the man who some say saved their convention?

Though it is often customary for the host governor to welcome delegates to his state — even if he is from the opposing party — as of press time Friday, Romney had “no speaking role” at the Democratic fete, according to his spokeswoman.

Perhaps that is because Romney has had harsh words for Democrats and their presumptive home-state presidential nominee.

In a July 14 speech at the National Press Club, Romney said Kerry was “too conflicted” to be president.

Romney then light-heartedly said that he welcomed the Democrats to Boston to enjoy the nightlife and sights but predicted: “Unfortunately, their candidate will go down in ignominious defeat. I will do everything in my power to make [the convention] a great success — except for that part.”

But as the convention drew closer, Romney dropped his fighting attitude and told a Boston Globe columnist that he would not join Republicans in piling on Kerry this week.

“I want the city to shine, and the state to shine,” he told the paper.

Romney can afford to be magnanimous after stepping into the union dispute when Kerry, Sen. Edward Kennedy (D-Mass.) and the rest of the Massachusetts delegation, who are all Democrats, ducked, said Robert Zelnick, chairman of Boston University’s journalism department.

Boston Mayor Thomas Menino was “furious” with Kerry for backing out of a scheduled speech before the U.S. Conference of Mayors in deference to the police union, and Romney stepped in to fill the role, Zelnick said.

The image of Kerry kowtowing to the union contrasts sharply with that of Romney “who came riding on his white horse to the mayor’s assistance,” Zelnick said. “It endeared him to not only the mayor but to Bostonians and many people in the state who thought the police had gone too far.”

It also allowed Romney to bolster his image as a Republican who is willing to buck his party to serve his constituents, as Republicans no doubt would have relished the thought of the Democratic convention being brought to a standstill by union protesters.

“My first responsibility on being elected was to serve the public and to do the public good,” Romney told the Globe. “We have an event that could be the target of terrorism. I could not conceive of politics influencing my actions in that setting.”

Rumors have circulated since he won the governorship in 2002 that Romney has his eyes on a bigger prize, and his rising national profile, such as the Press Club appearance, has done little to refute them.

Combining the success he enjoyed heading up the Salt Lake City Olympics, which he parlayed into a successful gubernatorial run, with a winning re-election bid in 2006 might make him a very strong presidential candidate in 2008, Zelnick said.

“He might have the momentum to make a serious go in 2008,” he said. Romney “hasn’t done very much to [dissuade] people of that, other than to say he would stay in his current job” through the term.

Romney told reporters it would be a mistake for President Bush to drop Vice President Cheney from the GOP ticket — tamping down rumors he is interested in being the replacement — and he has said that he would not run for Kerry’s Senate seat if it becomes available.

Tim O’Brien, executive director of the Massachusetts Republican Party, does not deny that Romney could go further than Massachusetts.

“He certainly has the charisma and star power to do something else,” O’Brien said.

But despite Romney’s star qualities, O’Brien said the governor has assured state party leaders that he plans only to run for re-election in 2006, and he has also worked hard to recruit and fund more Republican candidates for the state Legislature this year. The GOP holds just 23 of 166 state House seats, and only six of the 40 seats in the state Senate.

In a direct slap to Romney, Democrats have steamrolled a veto-proof proposal through the Legislature that would call for a quick special election to fill a Senate vacancy, taking the appointment power away from the governor. Romney’s call for a compromise was rejected.

While Romney fashions himself as a moderate, some members of the Massachusetts Congressional delegation disagree.

Republicans have been successful at winning the Bay State’s governorship by separating themselves, and the state party, from the national party, said Rep. Barney Frank (D-Mass.).

But Romney has moved to the right, “eliminating that fissure,” Frank said.

Rep. Mike Capuano (D-Mass.), who may challenge Romney in 2006, was more blunt.

“I am a little surprised how strident he can be in regards to the [presidential] election,” he said.

If Romney really had the best interest of his constituents in mind, he would support someone from Massachusetts, regardless of party, for president over a candidate from another state, Capuano said.

Speaking of a parochial issue, the possible closing of the Hanscom Air Force Base in Bedford, which would be detrimental to the local economy, Capuano asked, “Who is likely to be more sympathetic?” — Kerry, or Bush, “who probably does not even know where Bedford is?”

Romney has been a vocal Kerry critic and partisan at times, but right now many Bay Staters are likely to echo the words of Boston Globe columnist Brian McGrory and see him as a pragmatic leader.

“The Romney that emerged [last] week,” he wrote, “was the Romney I thought we’d get back in the 2002 gubernatorial campaign: an intellectually secure businessman who eschewed partisanship for the common cause, results being more important than process, with plentiful credit to go around.”

Josh Kurtz contributed to this report.