PARIS -- Gianni De Michelis is a European with ambitions as grand as his waistline, which is in the late Orson Welles-early Luciano Pavarotti league. But the Italian foreign minister did not suspect that a small rock he helped dislodge a few weeks ago would touch off an avalanche that would sweep Margaret Thatcher from office and change the course of European politics.

De Michelis pleads not guilty when I suggest to him in conversation here that he and Prime Minister Giulio Andreotti set out to isolate Thatcher at the Rome European Community summit in October. "We told her we had {German} Chancellor {Helmut} Kohl's agreement and that she should bring Britain in," the agile Venetian says with the faintest of smiles. "She wouldn't. She isolated herself."

Typical Italian understatement. Thatcher immolated herself. She angrily rejected the Italian-designed plan accepted in Rome by Britain's 11 European Community partners to form a unified central banking system by 1994 and a blueprint for political union. With the rockslide under way, Thatcher ignored her advisers and continued to lash out at De Michelis, Andreotti and assorted "Europeanists" in England after she returned to London. That was finally enough for "the dead sheep."

An opponent once observed that being attacked by the seemingly mild-mannered Sir Geoffrey Howe was like being savaged by a dead sheep. That line unfairly clung to Sir Geoffrey until two weeks ago. Then he rose in Parliament to resign as deputy prime minister and to deliver a devastating denunciation of "the very real tragedy" of Thatcher's anti-European unity policies.

That set the stage for Michael Heseltine's challenge and Thatcher's forced departure. Tomorrow the avalanche is due to come to an end with the selection by Conservative members of Parliament of a successor to Thatcher. Whether the new Tory leader is Heseltine, Douglas Hurd or John Major, Britain is now certain to draw closer to Europe than it would have under Thatcher.

Bad news for the special relationship between Washington and London? Not really. The Bush administration has been quietly encouraging Britain to get inside the EC tent and fight rather than stand outside and hurl insults. The EC will be able to draw on Britain's strong traditions of parliamentary democracy and free trade as it goes about drawing up continental institutions for the next century.

Depending on her mood and audience, Thatcher had dismissed the idea of European institutions as fanciful fairy tales or as dangerous leftist behemoths that would crush the British monarchy and parliament. Her Conservative Party rivals increasingly disbelieved and then discredited those visions.

They saw a dynamic new EC coming into being that would marginalize London's banks and financial markets if Britain stays out. They saw that they could help keep Eurocratic central planners from becoming the dominant forces in the community. Britain can change Europe as much as Europe can change Britain -- if it moves now.

Kohl is preparing a major push for expanding the powers of the European Parliament and making it the core of a European political community. This is the quid pro quo Kohl wants from his partners for his agreement to the 1994 start for the centralized banking system.

Re-enter De Michelis, a member of the Italian Socialist party, to suggest to us why: "Helmut Kohl knows that he will be the leader of Europe when Europe exists politically. The German chancellor is also the head of the most important political grouping, the Christian Democrats, in the community. Key decisions are going to be made at the party level, both in the European Parliament or in governments."

That is, all politics is local. The Germans have experience with a strong party and parliamentary system and can expect to dominate the new European political system. Not so accidentally, the Italians are also ruled by a coalition led by the Christian Democrats and know a lot about running party machines and parliamentary governments.

The chief resistance to such a strong EC parliament will come from France, which lacks both Christian Democrats as an organized force and a strong parliamentary system. The French will press to keep power in the hands of the EC heads of state, meeting as a group, and the Community's Commission.

Post-Thatcher Britain could be a counterweight to France in the gathering debate over dividing power between the parliament and the executive. Later, Italy would presumably find a constructively engaged Britain useful in balancing off Germany in the parliament.

De Michelis states the goals of the December EC summit that he and Andreotti will host in Rome far more modestly and elliptically than that. But as Margaret Thatcher discovered, this Italian is good at rolling small rocks a long way and making big noises.