Split among Brazil's Social Democrats clouds their chances of naming president

A split this week within Brazil's ruling Social Democratic Party has clouded the party's chances of designating who will become the nation's civilian president next year.

Until the split emerged, it seemed almost certain that the Social Democrats would be able to name their candidate as president because the party dominates the Electoral College. (The college, made up of elected representatives of the federal and local legislatures, elects the president.)

The split surfaced after a stormy meeting of party leaders over the issue of whether to hold primary elections to choose the party's candidate. Three of the Social Democrats' potential candidates favored holding primaries. But a fourth, former Sao Paulo State Gov. Paulo Maluf, backed the present system of selection by party delegates at a national political convention.

The rift between the ''Malufists'' and supporters of the other contenders, which has been simmering beneath the surface for some time, now looks to be irreparable.

Social Democratic Party (PDS) leader Jose Sarney resigned his post this week, saying he no longer felt able to keep the party united. More significantly, a key PDS presidential aspirant, Vice-President Antonio Aureliano Chaves, is threatening to set up his own party.

Mr. Chaves is widely thought to have more popular support among the general electorate than Mr. Maluf - and thus might benefit from a party primary. Party insiders say Maluf has campaigned hard to gain support of PDS convention delegates, and therefore stands to benefit by a party convention. Ten pro-Maluf members of the party's 15-member national executive committee refused to vote on the proposal for a primary.

The Electoral College is scheduled to choose Brazil's next president in January 1985 - the first civilian president in 20 years. The current military government is allied with the Social Democrats. The opposition's bid to initiate a popular direct election of the president was defeated in Congress last April. If the Social Democrats do not unite behind a candidate in the Electoral College , the chances of other parties are at least somewhat enhanced.

But the opposition represents a wide range of views. Unless it can win over someone like Chaves, it remains unlikely to present a serious threat to the ruling PDS.

Chaves has been criticized for trying to keep a foot in both camps: He is the only PDS candidate to back the opposition's drive for direct elections, while remaining vice-president of the military-backed government.