New Zealand turns to old-style battler for the underdog

David Lange, New Zealand's new prime minister after the July 14 general election, is a self-described middle-of-the-road socialist. He is also an old-style battler for social justice, the poor, and underprivileged.

Before entering politics only seven years ago, Mr. Lange (pronounced Long-ee) was a lawyer who eschewed the rich pickings of corporate advocacy to represent the needy in court. His eloquence and ability could have earned him a minimum of

During the election campaign he announced he was giving up the $11 weekly family benefit he gets for his three children (a state grant of $3.70 goes weekly to all parents for every child) because with his present high income it was embarrassing when there were so many needy.

Lange is a Methodist lay preacher whose socialist attitudes were formed as he watched his father, a doctor, administer to the poor in Auckland.

His own parliamentary constituency, an Auckland suburb, is one of the poorest in the nation, with high populations of underprivileged Maoris (native New Zealanders), Pacific island immigrants, and pensioners.

There, he said recently, ''you meet all the powerless, all the moneyless, and the hopeless. And you think about it and you get mad about it. That's why I am in politics.''

Lange, New Zealand's youngest prime minister in 100 years, has had a meteoric rise. Entering Parliament at a by-election in 1977, he became the Labour Party's deputy leader in two years and leader only 18 months ago.

It happened because party officials were desperate to find a winner to replace former Sir Wallace Rowling, a former prime minister who had lost three elections to the National Party's Sir Robert Muldoon, the man Lange ousted.

Lange, young and dynamic, quickly established himself as the best orator in Parliament.

He also had enormous presence, reminding people of the charismatic Norman Kirk, Labour's last elected prime minister, who died in office in 1974.

Losing 150 pounds was just part of Lange's transformation; a styled haircut, rimless spectacles, and well-tailored suits also improved his public image.

Party kingmakers worked on his oratory, better suited to a courtroom or Parliament than a public platform or television. He learned to cut the rhetoric, keep his expressive arms still, and talk in terms that the ordinary guy in the street could understand.

Some of the hype embarrassed Lange, including an election flyer which likened him to John F. Kennedy. ''I didn't have anything to do with that,'' he said.

Lange is not without his detractors, who regard him as shallow and question his lack of political experience. Few doubt he became prime minister because voters were more tired of Sir Robert than enthusiastic about David Lange.

Sir Robert, long ago eyeing Lange as a serious challenger, is one of his fiercest critics, dubbing him during the campaign a ''bumbling incompetent'' and nothing more than ''a brilliant entertainer.'' Sir Robert made Lange's inexperience his key campaign theme.

Independent commentators accuse Lange of inconsis-tencies, contradictions, and flowery generalities. They say his lack of experience in backroom politics will make it hard for him to keep a Labour government, with its traditional batch of strong-willed individualists, in line.

The new prime minister already has an heir apparent waiting in the wings in the person of party president James Anderton.

A longtime party activist who is seen as being well to the left of Lange, Mr. Anderton entered Parliament in a safe Labour seat this time and is regarded as the next leader, should Lange not make a go of things.

Lange's election theme was ''bringing New Zealand together.'' His style, he says, will be consensus government, healing rifts between employers and labor unions driven by an autocratic Muldoon administration. His aim is the traditional socialist target of redistribution of wealth.

Overseas, he seeks ''an independent international affairs policy, made in Wellington, not in Washington or London.''

His declared ''abhorrence of war and destruction'' is behind an antinuclear stance which signals an early collision with the United States over the ANZUS defense alliance that links his country with the US and Australia. US Secretary of State George Shultz is in Wellington for a two-day meeting of the alliance.

Above all, his foreign policy will reflect his personal concerns of social justice, with a new accent on the Pacific region and the third world.

''The type of society Labour is seeking to mold in New Zealand - a society free of conflict and the injustices of racial prejudice and economic deprivation - is also the type of international community we will be playing our part to create,'' he says.