The Peronist victories in Argentina's recent national and provincial elections cannot fairly be criticized as a "move toward the darker and more adventurous alternatives {to democracy} that have always meant trouble for Argentina" {editorial, Sept. 8}. President Raul Alfonsin and his Radical Party deserve much credit for promoting democratic norms. One of these is the freedom to vote for the civilian opposition. More than Peronism, the absence of a credible civilian alternative threatens dark and adventurous military coups.

The Argentina voters have spoken. It would be far more destabilizing were they unable to vent their dissatisfaction with current economic policies at the ballot box. It is a measure of President Alfonsin's success to date that the Peronist sweep did not produce even the whiff of a coup. The last civilian president to reach a fourth-year election -- Arturo Frondizi in 1962 -- was ousted by the military just after a similar Peronist victory.

The Post is right to worry about the Peronists' attachment to democracy. But Peronism is changing. Its electoral defeats in 1983 and 1985 spawned a strong "renewal" branch within Peronism, which opposes the strong-arm street tactics of the Peronists of yore. Since the Peronists remain the only credible civilian alternative to the Radicals, democracy's best hope is to see this renewal branch prevail. That will help Peronism evolve from a mass movement into a political party, with a vested interest in the continuation of civilian government. The longer that elections and not street rallies are where the action is, the more likely that the renewal branch will win the bitter struggle within Peronism.

Last month's elections served the purpose of midterm elections in any democracy: to jolt the ruling party out of complacency and to induce the opposition to behave responsibly in the hope of coming to power at the next election. The Radicals lost, but democracy won.

DANIEL B. PONEMAN Washington