Feisty Chilean tries to hasten end of junta. Back from exile, Zaldivar chips rust off civilian politics

He stands a mere five feet, two inches tall. But in the eyes of many of his fellow countrymen, Andres Zaldivar Larrain has the stature to challenge Chile's military dictatorship, headed by Gen. Augusto Pinochet Ugarte.

A former Chilean senator and cabinet minister, the feisty Zaldivar returned to Chile in August after three years of enforced exile in Spain - and promptly waded into the mushrooming effort to end military rule here.

In his view, now is the time to stand up to what he terms ''the worst government in the history of Chile.''

Mr. Zaldivar says he has no illusions that the task of returning Chile to civilian hands will be easy or that it will be accomplished soon. Rather, it is likely to be ''a gradual process,'' he says. But the process, he adds, ''must be speeded up.''

That is also the view of the Alianza Democratica, a loose amalgam of six political parties that includes Mr. Zaldivar's Christian Democratic Party, for decades Chile's largest political grouping.

Although he does not now hold office in the local party, Mr. Zaldivar is head of the worldwide Christian Democratic International, and plans to open its world headquarters in Santiago soon.

That fact should strengthen the opposition movement here by directing a lot of attention to Chile; it should also add to Mr. Zaldivar's local luster.

He already is the one individual most Chilean Christian Democrats would like to see lead their party. Long a force in the party, he is in many ways the logical person to inherit the mantle left vacant 18 months ago with the passing of former President Eduardo Frei Montalva.

Mr. Zaldivar was Mr. Frei's top lieutenant, particularly in the years after the Frei presidency, which ended with the election in 1970 of socialist Salvador Allende Gossens. It was the Allende presidency that the military snuffed out in seizing power in 1973.

The years of military rule have been difficult ones for the Christian Democrats and their colleagues. The party was left in limbo when its activities were proscribed by the military. But Mr. Frei, with Mr. Zaldivar's active assistance, managed to keep the party cadre active and it, in turn, kept in touch with the grass roots of the party.

The military sent Mr. Zaldivar into exile in 1980 over a newspaper interview with a Mexican reporter that turned out to have misquoted Mr. Zaldivar. The military government frequently seemed to grasp at straws to undercut Zaldivar - even jesting about his short height.

But there is tremendous enthusiasm among Christian Democrats over Zaldivar's return. Yet the politician is aware that the years of military rule have left some of the party apparatus rusty. He also knows that 43 percent of all Chileans have never voted in a presidential election.

''There's a generation out there,'' he says, ''that needs to be brought into the political spectrum.''

At the moment, the Christian Democrats are headed by Gabriel Valdes Subercaseaux, foreign minister under Frei and subsequently a United Nations official. An able thinker, he has not had the active political role so familiar to Mr. Zaldivar. The two are friendly - and there seems little likelihood that there will be any clash between them.

As one top Christian Democratic leader said, ''They both know that the enemy is the government, and that is where they and all the civilian politicians are going to direct their fire.''

There is, however, some rivalry among the six members of the Alianza Democratica. The Christian Democrats are clearly the dominant party. But the other political groups, some to the left and some to the right, want a strong political role and the Christian Democrats are going to have to share power.

For Mr. Zaldivar, that is proper. He says it would be a ''grave error'' for the Christian Democrats to try to control a future government. He favors a ''consensus government.''

''The problems of Chile are so enormous in all fields - political, economic, and moral - that we need a common program. The problems are the result of Pinochet's rule,'' he adds. ''It will take a common effort to restore true democracy.''