Many Spaniards profess to be unsurprised that the transition to democracy since the death of Generalissimo Francisco Franco in 1976 has been so smooth, but hardly anyone expected that the country would be on the verge of transforming itself peacefully from one of the world's most rigidly centralized states into something like a federal union.

As in France and England, the energies of Spanish kings were spent turning Spain from a collection of warring provinces and principalities into a centrally governed state.

Historically centralization in Spain was identified not only with the idea of the modern nation-state, but also with the political right and its traditional institutions - the monarchy, the church and the army.

It is probably only the name of Franco's successor, King Juan Carlos, on the royal decrees granting provisional autonomy to Catalonia and the Basque country - who separatism kept them in continual conflict with the Franco government - that has made it tolerable to the army, which regards itself as the guarantor of national unity.

The experiment in regionalism is also being looked upon with some disquiet in the rest of Western Europe, where most countries are beset by troublesome regionalist movements.

French President Valery Giscard d'Estaing, who came into power preaching decentralization has just made it clear in a tour of Corsica, a separatist hotbed, that he has reversed himself and is not at all sure that regional government is such a good idea.

The French are also worried about separatism in Brittany and the potentially dangerous example the separatists might give to linguistic minorities on almost all of France's frontiers - the Flemish of Flanders, the Germans of Alsace, the Italians of Nice and Savoy, the Provencals and the inhabitants of France's own Basque country.

The English have recently seen that nationalism was waiting to be rekindled in Scotland, Wales, Cornwall and the Isle of Man, not to speak of Ulster. Belgium's unity is plagued by its periodically warring Flemish and Walloons.

The exact form of regional autonomy in Spain has not been spelled out and is the most controversial question facing drafters of the new constitution. Premier Adolfo Suarez is widely suspected of encouraging all of Spain's traditional regions to seek autonomy as a way of reducing the impact of giving it to the Basques and Catalans, the only mainland autonomists with recognized languages of their own.

The transition from dictatorship to democracy has happened with break-neck speed, yet, there seems to be fairly widespread disillusionment that democracy has happened with breaktry's problems overnight, least of all high inflation and unemployment. So, the focus for hopes by the large proportion of the 36 million Spaniards who are unhappy with their lot has shifted from democratic central government to some vague expectation of salvation by the new regional autonomias that Suarez has offered.

Manuel Fraga Iribarne, a former Franco Cabinet minister who describes himself as the leader of the "civilized right" in the provisional parliament, said in an interview, "In the United States, federalism was a way, as you Americans put it, 'to form a more perfect union.' But it makes no sense to divide a unitary state. What happens with the regions is our most serious problem. Suarez doesn't know what he wants. All he does is surrender continually to the demands of the Basques and Catalans."

Blas Tinar, the leader of the small but vigorous fascist party, goes even further, speaking of "the surrender of Spain to autonomist governments which hopes to become independent states." They are a vehicle, he said, for Marxist Parties to take over the country. Even before a final text is ready, Tinar's New Force Party is covering the country with graffiti reading, "No to the Constitution."

Even Fraga recognizes that there must be some regionalism, but he advocates that it be along the lines of the weak Italian regions that took 20 years to set up after they were first provided for in the Italian constitution. He said there could also be special arrangements for particular regions, like the ones for Sicily and Italy's German-speaking Trentino region.

Spain's Communists are being very prudent. Ramon Tamames, one of the Communist constitutional negotiators in the small parliamentary committee working on the tex, in an interview that the draft will be ambiguous and that the final form of regional autonomy will be left to detailed negotiations over an enabling law.

Tamames displayed vivid awareness of the anxiety over the issue in an army that fought under Franco to reduce the Catalan and Basque bastions of republicanism. Rightists identity the two regions with republicanism and the left.

When the Spanish Civil War broke out in 1936, Franco expected the heavily Catholic Basques to side with him. The special vengeance that Franco wreaked on the Basques when they did not is offered as an explanation for the refusal of ETA, the Basque independence movement, to lay down its arms even now that there is a government in Madrid ready to compromise.

Tamames, the Communist, said he thought regionalism is far less of a threat to national unity now than under the republic.

"The integration of Spain is much stronger now than in the '30s," he said. "Then, we had no electricity, television. There were not the same population flows between regions. We did not have a national market. Even the spread of the Spanish language has had a big boost in the past few years. Catalonia is a bilingual country today. So is the Basque Country."

The Madrid government has been fortunate so far that the Catalans have been especially moderate under the leadership of 78-year-old Josep Tarradellas, who was called home from exile by Juan Carlos to head the reconstituted Catalan parliament.Tarradellas has turned the king's calculated risk into a triumph.

There are those who are already thinking that after the nationalist movements have been neutralized, regionalization will pose serious practical problems.

"In the long run," said Cabinet minister, "Spain's worst problem is Andalusia. What do we do about poverty and unemployment there?" Spain's southernmost region, it is comparable in its conservative peasant traditions and economic backwardness to Italy's.

In a country beset with major economic worries, the disadvantages as seen at the Finance Ministry of giving up tax revenues to the regions and of finding money to help them set up new administrative structures seem to outweigh the advantages. Ministry officials also wonder what will happen to the bureaucracies in Spain's 50 administrative provinces.

There will probably be 13 mainland regions if Navarre accepts the Basque efforts to absorb it, plus the Canaries off the Atlantic shores of Africa and the Balearic Island in the Mediterranean.

"Catalonia will take care of itself," said the Finance Ministry man. "The standard of living in Barcelona is comparable to Milan's," he said, likening Spain's northern industrial metropolis to Italy's. "But I'm not so sure about the other regions."

Catalonia, thanks to the predominance of Barcelona, is also the only region that does not have an argument going about where its capital should be. In Andalusia, regional authorities have agreed to split up the functions of local government among the seats of its eight administrative provinces.

The Basques have proposed that their capital be in Pamplona. The only trouble is that Pamplona is actually the capital of neighboring Navarre, which the Basques hope to annex in a forthcoming referendum.

Not to be outdone, New Castile, the flat region surrounding Madrid, wants its autonomy recognized from the regions it has conquered and dominated. Naturally, the citizens of Toledo, the original royal capital, are pressing their claims to be the regional capital voer Madrid.

Says Tierno Galvan, Spain's leading constitutional law professor, "We can't predict where all this autonomy is leading. Today, it is positive. It provides for decentralization and guarantees of democracy. Tomorrow, it could create economic strains among the regions and create a new layer of bureaucracy."