BRASILIA -- Legislators on a key constitution-drafting committee voted narrowly yesterday to limit the term of President Jose Sarney and his successors to four years, bringing Brazil's simmering political crisis to a boil.

The 48-to-45 decision marked a humiliating defeat for Sarney, who had lobbied hard to stay in office longer and warned last week that he would consider himself at "war" with any legislator who voted for less than a five-year term.

If, as expected, the four-year period is endorsed by the full Constitutional Assembly, it will mean presidential elections in Latin America's biggest nation sometime next year -- the first direct election of a head of state in Brazil since 1960.

Sarney, 57, a former governor of the small northeastern state of Maranhao, assumed the presidency in 1985 when Tancredo Neves, who had been confirmed by an electoral college to lead Brazil's democratic transition, died before taking office. Sarney was to have been vice president.

The president's popularity soared last year in the wake of an economic plan that temporarily choked hyperinflation. But as prices, debt, political squabbling and reports of official corruption surged again this year, the public's regard for the poet-politician sunk to new lows.

Widespread frustration and discontent with Sarney also lay behind another highly charged decision this month by the constitution-drafting committee to recommend a new form of government.

Over Sarney's opposition, committee members voted to replace the country's traditional presidential system with a parliamentary one, in which a prime minister representing a congressional majority would exercise real executive power alongside an elected president.

Sarney controls neither the huge Brazilian Democratic Movement party nor its smaller, more conservative partner in government, the Liberal Front. His administration has been crippled by fighting between the coalition parties over jobs. Repeated attempts by Sarney to build a personal base of support outside regular party lines have fizzled.

Nonetheless, until recently, many of Brazil's military and business leaders and powerful state governors had favored waiting another two or three years for elections, hoping to improve their campaign chances against leftist and populist groups. But with the president's authority eroding to alarming levels, key political and business figures this month began joining the ranks of those calling for elections next year.

Highlighting the government's weakening grip, the Brazilian subsidiaries of Ford Motor Co. and Volkswagen decided 10 days ago to defy official price-control policy. Autolatina, the holding company that groups both subsidiaries, announced price increases of 26 to 30 percent, far above the 17 percent authorized by regulators.

Many analysts see Brazil's political crisis as both cause and effect of its economic troubles, as well as an important contributing factor to deteriorating relations with the United States. But perhaps most disturbing for the country's long-term political definition is the fact that tensions between Sarney and Congress have dominated the writing of the new constitution. The Congress in joint session is doubling as a special Constitutional Assembly.

Launched nine months ago, the drafting process had been conceived as a vehicle for consolidating democracy and giving new form to Brazilian politics, economics and social programs after two decades of military rule. Instead, it has turned into a messy and disruptive exercise, destabilizing the transition period and tripping this normally upbeat nation into an uncharacteristic malaise.

In the absence of respected presidential leadership or strong congressional direction, bargaining over numerous mundane issues -- which legal scholars say would be better addressed in ordinary legislation rather than a constitution -- has consumed the assembly's time.

Military commanders, who have withdrawn only to the shadows of power, not to the margins, have voiced concern about the way things are going. Businesses, both domestic and foreign, are stalling investment decisions until a clearer picture emerges of what the new constitution will say.

"The process has been too complex and prolonged for this country," said a prominent political scientist. "People have the impression nothing real is being discussed. They have the idea the process is somehow blocking real decision-making."

Even in the best of times, the balancing of interests in this land of enormous contrasts would be a daunting task. Brazil contains not only the skyscraping economic capital of Sao Paulo, with 14 million people, but thick rain forests populated by primitive tribes. With 140 million people, it is the world's third most populous democracy, behind the United States and India, and it has the 10th largest economy, yet the majority of its people remain poor and hungry.

Each of the several constitutional drafts so far has addressed a list of the issues that have polarized Brazilian politics for generations: land reform, labor laws, state control of the economy and the role of the military.

Eager to exercise newly granted freedoms, everyone has wanted to get into the act. From landowners and corporate chiefs to unionists and Roman Catholic priests, Brazilians have crowded the broad, stadium-style corridors of the modernistic congressional building to promote favorite causes. Lobbying, once a dirty word here, has become a necessary political activity.

"After years of indifference, everyone now wants to participate, every group wants to mobilize," said a senior presidential aide. "It's difficult in such a situation to impose solutions. What characterizes the Brazilian political situation at the moment is a difficulty in building a consensus."

Sarney has not been alone in failing to provide firm stewardship, analysts say. Leaders of the Brazilian Democratic Movement, which controls both congressional chambers, have served mostly as moderators and arbiters, not political pacesetters.

The party, swollen by landslide victories in gubernatorial and congressional elections a year ago, lacks clear definition, encompassing leftists as well as the supporters -- like Sarney himself -- of former military regimes.

Compounding the political mess has been the economic crisis, triggered by the government's ill-fated decision last year to keep wage and price controls in place too long. That sustained a domestic buying boom that ate away at exports.

A shrinking national trade surplus and dwindling hard-currency reserves pushed Sarney in February to suspend payment on Brazil's foreign commercial debt, the largest in the Third World. Recurring inflation, sluggish growth and capital outflows have plagued the country since, and accelerated Sarney's political decline.

Brazil has had seven constitutions in 165 years of independence. In the past, small selected groups did the drafting behind closed doors. But not this time. Discarding historical precedent -- and the example of foreign nations -- legislators have chosen to create a constitution in public and from scratch.

Lawmakers here began without a draft and set up eight commissions and 24 subcommissions. The work of these groups was debated and rewritten by a 93-member "systematization" committee, which was due to conclude its deliberations yesterday following the vote on Sarney's term. Its draft will be presented to the 559-member assembly for yet more debate, amending and voting.

All in all, the constitutional effort has taken on the tone of Carnival. "What is most striking about the entire process," observed the daily Folha de Sao Paulo in a recent editorial, "is not the feeling of wasting time but the lack of grandeur with which important topics are being treated. In effect, the members of Congress do not hesitate to change positions, motivated by opportunism, corporate pressure, personal interests and the immobility of government."

Having already broken a series of deadlines, assemblymen hesitate to predict when they will finish the document -- or even what political bent it will take.

Leftists on the systematization committee have won approval of articles strengthening agrarian reform, assigning distribution of petroleum products solely to state-controlled companies, providing firmer job guarantees, shorter work weeks and longer maternity leaves.

Alarmed centrists and rightists are mobilizing under the banner of a grouping called simply the Center to try to roll back these measures in the plenary session.