La Scala Mobile sounds like an aria from an Italian opera. Actually, it has been, until quite recently, as firmly embedded in the Italian economy as arias are in Italian opera. La scala mobile, "the moving staircase," is an automatic increase in wages to compensate for increases in the cost of living. As is often the case with indexation, the particular formula used tends to become unduly generous, and its application a year or so after the inflation has occurred tends to cause further inflation. Yet indexation usually remains politically popular. How many voters are willing to give up something that protects them against (or puts them just a little ahead of) inflation?

The answer, from some 33 million Italians voting Sunday and Monday, is heartening: a solid majority. Socialist Prime Minister Bettino Craxi and his five- party government had the courage last year to cut 4 percent off the "moving staircase." The Communists -- usually the second-largest party and in the 1984 European election the largest -- responded by forcing a referendum to restore the 4 percent. The Communists had little support; of Italy's other parties, only the neo-Fascists followed their lead. But their hope obviously was that the ordinary people of Italy would vote their pocketbooks. To some extent they did: the approximately 46 percent who voted yes exceeded the percentage of those who have voted for the two extreme parties in Italian elections. But the more important fact is that an unambiguous majority voted no. The Communists, on about as politically attractive an issue as they could hope to find, nonetheless lost.

And Mr. Craxi won. He had threatened to resign immediately if his side lost, and that might have been an even greater loss than the point-or-so rise in inflation a restored scala mobile would ve caused. Mr. Craxi's government is one of the longest-lasting in postwar Italian politics, and has courageously tackled many of the country's major problems. Everyone in the coalition has held everyone else's hands firmly as they all jumped together, cutting industrial subsidies, scaling back social benefits and attacking indexation. The Italian government now has major achievements to its credit: it has controlled terrorism while respecting civil liberties; it has produced economic growth while lowering inflation; it has maintained its commitments to the Western alliance. Italy has proved to be one of the most stable of Western democracies. Its voters' rejection of the Communists' scala mobile referendum is welcome evidence that the voters are willing to endure some pain in the struggle to bring inflation under control.