EVEN BY Italian-government standards, the scandal erupting in Rome is bizarre and melodramatic. There's the hint of a possibility this time that it might even knock Italian politics off the familiar circular track of weak and defensive governments, beset by unmanageable crises, that soon fall only to be replaced by further weak and defensive governments.

Over the years, Italian politics had developed a rich lore of dire conspiracies. There are code-named villains -- remember Antelope Cobbler in the Lockhead affair? -- and sinister relationships to various intelligence services. There are always high political connections -- although here the present case outdoes itself -- and huge amounts of money allegedly washing back and forth. Usually, after the first explosion of charges in these incidents, the prosecution goes into slow motion -- frequently so slow that nothing is ever resolved. The cumulative effect has been only to deepen the distrust, not to say cynicism, with which Italian voters seem to regard their political leadership. But it's at least conceivable that things will be different this time.

For one thing, there's that astounding list of nearly a thousand names published by the government. The people included -- two Cabinet ministers among other politicians, plus a wide assortment of military officers, businessmen and financiers -- are supposedly members of a Masonic lodge that had degenerated into corruption on a very big scale. There are allegations of bribery, illegal currency manipulation and massive diversions of tax revenues.

For another thing, the government has fallen with more than the usual accompanying rancor.Perhaps it will once again be reassembled in a form very much like the last one. Italy is a country in which Humpty Dumpty has been put back together more times than he can count. But it's worth considering the outside chance that the long dominance of the Christian Democratic Party may be coming to an end. The party has declined into a condition of feebleness that is proving exceedingly costly to a modern industrial country that is nearly as rich as Britain. The Christian Democratic Party has provided every prime minister, and has been the prevailing force in every Cabinet, since 1945. One secret of its success has been the failure of Italian politics to provide any non-Communist alternative.

But Italian politics sometimes resonates strongly to events elsewhere in Europe, and the Italian left seems to have drawn new energy from the election of a Socialist president in France. The ambitious Italian Socialist Party has been gaining strength for some time, and now appears to be pressing for a larger role. The Communists, having lain low for several years since the collapse of the Eurocommunist movement, are now talking more aggressively about participation in future governments. The revelations about the Masonic lodge did not originate in the left. But the extent of the scandal, and the speed with which it brought the government down, now create an unusual opportunity for the Italian left to exploit the French example.