The party elders are watching. They’re watching television, and they’re watching the Democratic gubernatorial candidates, and there had better not be a disparaging word about any of them.

In the long war against negative advertisements in politics, there never has been anything quite like the board of elders the Democrats have set up as they work to win back the governor’s office on Beacon Hill for the first time since Michael Dukakis held it, an eon ago in 1991.

This is how it will work: If one of the three candidates for the Democratic nomination steps out of line, the elders will step all over him. Or, as Philip Johnston, the party chairman, put it in a conversation the other day: “If you run very vicious ads in the last week or two, when your political consultants tell you to pour it on, you’ll hurt the Democrats’ chances of winning the governorship, and we’ll say something — and you’ll pay a price politically.”

Besides Johnston, the elders are Dukakis himself, Cameron Kerry (John Kerry’s brother) and Katherine Clark (a leading Democratic activist). All are political veterans, all have close ties to people in the three Democratic gubernatorial campaigns, all have no aversion to speaking their minds.

“The mere fact that we exist,” says Dukakis, whose presidential hopes were destroyed by a fusillade of negative advertisements in 1988, “may stop these attacks.”

The problem with negative advertisements, of course, is that, from the attackers’ point of view, they work. But attacks in a primary campaign can wound a nominee in the general election, and that’s what the Democrats are worried about. This is a special problem in Massachusetts, which has an especially late primary. It chooses its nominees Sept. 19. By comparison, Pennsylvania chose its nominees May 16.

“We have a late primary — very late — so we can’t afford any bloodletting,” says Dukakis.

This isn’t the first time politicians have tried to rein in the negatives. In 1988, Democratic Party chairman Paul Kirk Jr. looked at how, four years earlier, Sen. John Glenn of Ohio and Sen. Gary Hart of Colorado stigmatized former Vice President Walter Mondale of Minnesota as a tool of special interests — a charge that President Reagan was only too happy to emphasize in the general election. So he created a unity task force and told his party’s presidential candidates that they would only weaken their November chances if they weakened their nominee through negative ads.

A decade ago, in an Iowa congressional district so big that it measured 14,000 square miles, two House candidates swore off negative ads. The truce between Leonard Boswell, who was the president of the state Senate, and Michael Mahaffey, a former GOP state chairman, lasted most of the campaign. Mr. Boswell prevailed and still serves in the House.

Then, four years ago, as part of the McCain-Feingold campaign-finance law, federal candidates’ broadcast advertisements were required to state “that the candidate has approved the communication.” That accounts for the familiar phrase that made up the tagline in so many campaigns two years ago.

This is an even bigger step, and the irony is the involvement of Dukakis, who seemed to be cruising to the White House until Vice President George H.W. Bush and his consultant produced the most effective negative ad in history, the one featuring the convicted killer Willie Horton, who was furloughed under a Massachusetts program and then brutally beat a man and raped a woman. Dukakis spent much of the rest of the campaign explaining his position on the furlough program.

“It was my own damn fault,” Dukakis said. “The lesson of my campaign is to have a plan and to be ready for attacks. There comes a point where you have to defend yourself, and unfortunately that was something I did not understand in 1988. When a guy from Boston, a city with a low murder rate, loses to a guy from Houston, with a high murder rate, maybe you shouldn’t get elected. But that was the finals. This is a primary, and we can’t afford the divisions.”

Democratic divisions hurt Scott Harshbarger, the party’s gubernatorial nominee in 1998, and Shannon O’Brien, the nominee in 2002. So far the three candidates — venture capitalist Chris Gabrieli, former Justice Department official Deval Patrick and state attorney general Tom Reilly — have been behaving civilly.

But the three of them will almost certainly spend as much as $15 million in the run-up to the primary, and past practice shows that when the going gets desperate, the campaigning gets nasty. How will the elders define what is unfair or overly negative?

“It’s like the Supreme Court and pornography: We’ll know it when we see it,” says Dukakis, who was in Massachusetts politics for three decades. “But mostly we’ll be a restraining influence. These candidates will not want to run into a buzz saw from us in the last few weeks of the campaign, and therefore they’ll restrain themselves. Can’t hurt, might help.”

National Democratic officials are watching this council of elders to determine whether they might convene a similar one as the party seeks to win back the White House in caucuses and primaries that begin only 18 months from now.

“You never know what the ultimate effect of this will be,” said Kirk, who was Democratic national chairman between 1985 and 1989. “But given the tone campaigns take — raising all this money to buy negative ads to demonize the other guy — this can’t be bad.”

Maybe not. Johnston calls the council of elders a “deterrent.” Sometimes, as the Cold War shows, sometimes deterrents actually work.