Some days, Tancredo Neves adopts the role of a master political insider, secluding himself with the elite voters of Brazil's electoral college who are to choose a president.

On others, he campaigns for the job like an updated populist, jetting to a farmer's rally and assuring the crowd that "there is no better political advice than the plazas full of people."

Neves claims the standard of popular discontent with Brazil's military government, but simultaneously depends on the backing of scores of congressmen from that military government's party. He strives to charm ideologues of the right and left but insists on preserving his own political agenda.

Neves, in short, has become the candidate of both conciliation and contradiction in Brazil's shift to civilian government. With 50 years of political experience and a cautious but persistent style, this 74-year-old opposition leader is betting that his country's desire for political consensus after two decades of military rule will propel him to power.

"Periods of political transition are always accompanied by measures that make an accommodation possible between the era that ends and that which begins," Neves said at a press conference. "And this is always done by a broad agreement."

Neves' emergence as a contender against the government's official candidate in the January election, Paulo Maluf, seemed to be shaped by equal measures of circumstance and patient maneuver.

As the popularly elected governor of Minas Gerais, a major southern state, Neves supported the opposition's drive for direct presidential elections this year, while discreetly allowing more militant politicians to assume its leadership.

When a constitutional amendment establishing the direct vote was defeated in Congress, Neves assumed the leadership of opposition sectors arguing that the movement should seek to build an alliance that could defeat the government's Social Democratic Party among the 686 congressmen and state representatives in the military-designed electoral college.

As a result, when civilian moderates of the ruling party rebelled against the prospective nomination of Maluf, Neves was perfectly positioned. He quickly allied his Brazilian Democratic Movement with more than 40 Social Democrat dissidents, led by Vice President Aureliano Chaves, and in a matter of weeks became the favorite.

"It was a spectacular piece of political work," said a diplomat. "He just waited while everyone else did their thing, anticipating what would happen, and when the moment was right, he made his move."

His formal nomination in August, politicians here say, had far more to do with political compromise than public popularity. "He was basically the person all the traditional political elite could agree on," said Walder DeGoes, a political scientist.

However, Neves' supporters maintain that he has established the coalition of national unity that the country has been looking for. They cite public opinion polls showing Neves with the support of 60 percent or more of the general population, which, though unable to vote, has turned out by the millions for opposition demonstrations.

"There are moments in history when a country needs a great agitator, and moments when it needs a great mover of masses. And then there are times when it needs someone to harmonize its conflicts," said Jose Sarney, who served as president of the ruling party before defecting to become Neves' vice presidential candidate.

Neves' prestige among politicians depends to a large degree on his long record; he was elected to office in 1934 and has held several key positions. His most important role was as prime minister during Brazil's brief experiment with parliamentary government in the early 1960s.

Following the military coup, Neves refused invitations to join the government and remained a leader of the opposition. At the same time, he avoided intransigent resistance to the government and was known for his willingness to negotiate privately with several military presidents.

A short, soft-spoken man whose craggy features long have delighted political cartoonists, Neves has attracted much of his support on the strength of his position in the opposition. He has spent weeks privately bargaining with hundreds of politicians and businessmen, but his aides say he has avoided making specific commitments, leaving himself a margin for improvisation.

Many politicians and diplomats expect that Neves would implement a moderate government program. His advisers say he would strengthen social programs and seek to ease the burden of a four-year recession on the working class. They say he would not revise traditionally centralized development strategies nor reject the belt-tightening program that country has followed to satisfy the International Monetary Fund and banks holding its $100 billion foreign debt.

Neves has yet to define clearly a program for government, and his opponents say the omission is deliberate. "Neves doesn't have a program, and he can't have a program," charged Maluf in an interview. Only the lack of clearly defined positions, Maluf insists, allows his opponent to hold his unorthodox coalition together.

What seems to unite Neves' supporters, who range from communists to conservatives who still defend the military rule, is the goal of blocking Maluf -- whom they accuse of opportunism. Avoiding Maluf, they say, would ensure return to direct presidential elections in 1988.

Otherwise, the factions supporting Neves appear to have contradictory ideas of the policies and even the nature of the prospective administration. Opposition leaders to the left of the candidate frequently predict that he will be a transitional president, concentrating on political reforms and ultimately deferring, like a parliamentary president, to the winners of 1986 congressional elections.

Other politicians argue that Neves will turn his coalition into a powerful centrist political movement that will dominate the political future. "Tancredo is going to implement all of the ideas he has developed over 50 years in politics," said Israel Pinheiro, a ruling party congressman from Minas Gerais. "And to do that, he will build a great political movement that will outlast him by decades."