But arch-rivals and enemies sat side-by-side on the stage at the official opening of the Ted Williams Tunnel yesterday morning, and not even a freezing drizzle could dampen their camera-ready smiles.

That's because the project, from blueprint to fruition, spanned the administrations of five governors and six presidents, along with dozens of politicians and appointed aides who put their mark on the tunnel project but also helped keep it alive.

"Every once in a while, we do something together," said former Gov. Michael S. Dukakis. "Everyone was very gracious."

Would that the unity ran as deep as the tunnel.

Certainly, it had to be a tense troika in the lead car through the 1.6-mile tube, with Gov. William F. Weld behind the wheel and his two predecessors -- and bitter rivals -- Dukakis and Edward J. King sharing the back seat. Dukakis and King disagreed about the tunnel and just about everything else, and have barely exchanged a word since Dukakis won their rematch in 1982. King and Weld have an outwardly cordial relationship, even though King, a Democrat while governor but now a Republican, endorsed Democrat John Silber over Weld in the 1990 gubernatorial election.

King and Dukakis, however, may have shared one thought yesterday: that Weld was getting entirely too much credit for the first tangible fruit of the Big Dig -- championed, planned and funded by Democrats but built by a Republican state administration.

Weld was attuned to the rich ironies of the ride.

"They didn't seem too nervous, though I noticed Gov. Dukakis was the first to put his safety belt on," said Weld, who was behind the wheel of the inaugural convertible.

Others, perhaps seeing the tunnel opening as mostly Weld's show, passed on the whole thing. Sen. John F. Kerry, whom Weld is challenging next year, stayed in Washington and avoided the jockeying for credit altogether. Aides said he was busy working on budget measures.

But Mayor Thomas M. Menino stood his ground and said his piece, despite being frozen out of much of the tunnel-opening hoopla, including not having his name on the memorial plaque at the tunnel entrance. At the 11th hour, a second plaque, with the mayor's name along with those of other notables, was mounted.

Meanwhile, Weld's transportation secretary, James J. Kerasiotes, stood not far from Massachusetts Turnpike Authority Allan J. McKinnon; only days before, the two were shouting at each other on a talk radio program.

Notably, the Turnpike Authority was never mentioned in the speeches, despite its extensive work toward the tunnel opening and the fact that it will run the new tube.

And then there was Senate President William F. Bulger, sitting happily amid the political crowd he tweaks in his new memoir, excerpts of which appeared that morning in the Globe. He sat right next to Dukakis, whom he criticizes in his book as an early supporter of the Boston school desegregation busing order.

"You'll all be in my next book," chirped Bulger, who took over Kerry's slot on the speaking program. Come back next year, he then told the guest of honor, Ted Williams, who was known as the "Splendid Splinter" in his baseball-playing days, "and I think I can give you an honorary degree."

Bulger, with Weld's blessing, is the new president of the University of Massachusetts.

Notable no-shows

The just-beneath-the-surface tensions would have been even greater had a few more principals showed up -- most notably Kerry, whom Weld has challenged for the Senate.

Rep. J. Joseph Moakley, a Big Dig stalwart from the days of Democratic domination and Bay State clout -- the late House speaker Thomas P. (Tip) O'Neill helped save project funding more than once -- also stayed in Washington.

And Frederick Salvucci, transportation secretary under Dukakis and in many ways the chief architect for the Ted Williams Tunnel and the Central Artery depression, was stuck on a plane from Philadelphia, waiting to land at Logan while the Marine band played and the plaques were unveiled.

"We circled for an hour over Providence," Salvucci said, finally arriving after the event had ended.

Salvucci and Kerasiotes have an enduring rivalry. Kerasiotes made the only blatant jab of the morning, suggesting that the Weld administration saved state government from bankruptcy and Massachusetts from economic doldrums, as Dukakis stoically looked on.

The acrimony behind the construction of the Ted Williams Tunnel can be traced to several levels. One is simply differences about where the tunnel should go and how it should be designed. In an interview, former Gov. King essentially proclaimed that he still thinks his own tunnel plan would have been better.

Another level reflects philosophical differences between Republicans and Democrats. When Dukakis took office after defeating King in 1982, he "didn't want to hear anything about the third harbor tunnel," he said. "We have a third harbor tunnel. It's called the Blue Line."

Dukakis, a loyal subway booster, wanted more money spent on mass transit, as many Democrats did.

Republicans, on the other hand, tend to like cars. To many, a well-paved highway is often the only regular point of contact between voters and their government.

Salvucci, it seems, executed the bipartisan master stroke by linking the tunnel and the Central Artery depression, which creates open space, puts cars underground and may include a mass transit component linking North and South stations.

But the elbowing goes on, of course, in who gets credit. It was no accident, for example, that Lt. Gov. Paul Cellucci had a prominent speaking role, since the successful management of these huge public works projects could boost his anticipated campaign for governor.

But heaven forbid that such machinations should mar the bipartisan gloss of yesterday's proceedings.

"There's plenty of credit to go around," Cellucci said. "The commitment to do this came from both parties."

"Great projects have a way of bringing people together," added former New Hampshire Gov. John Sununu, with a smile.