TV looks at two Democrats of the past - Truman and Lowenstein

Two unique democrats - Harry S. Truman and Allard K. Lowenstein - are being honored with timely electronic eulogies next week. As the Democratic National Convention gathers momentum in San Francisco, these two uncommon politicians - the likes of whom will be difficult to find at any political convention in any year - are profiled in two very different televison shows: CBS Reports: The Legacy of Harry S. Truman (CBS, Wednesday, July 18, 8-9 p.m.) and Citizen: The Political Life of Allard K. Lowenstein (PBS, Friday, July 20, 10-11 p.m., check local listings).

Although the format of the two shows is very different, both have a great deal to say to committed observers in the current political atmosphere. Both men - Truman and Lowenstein - were devoted believers in the democratic process and lived a good part of their lives fulfilling that trust.

With Harry Truman, the course of history made it possible for him to discover and follow through on much of what he believed; as for Lowenstein, his political mission was cut short by assassination. But, although a superficial look at their backgrounds and records might not reveal it, in many ways Truman and Lowenstein were social and political brothers - concerned and yet pragmatic men who managed to dwell for most of their lifetimes in a kind of mythic castle constructed of their own convictions.

'The Legacy of Harry S. Truman'

Seemingly still in the running for the title of Mr. Avuncularity, Walter Cronkite pushes both Uncle Charlie Kuralt and Uncle Bill Moyers off the ''Crossroads'' show next week for a special Truman edition.

Mr. Cronkite points out that although Truman is thought of as a man who brought simple humanity to the office of president, the fact is that he was a complex human being, a strong President who changed America's course in the world.

Some of Truman's closest advisers appear on camera - Clark Clifford, George Kennan, and Leon Keyserling - and seem to try to give balanced pictures of their boss, which, naturally, tend to border on hero worship. Cronkite manages to get them to make honest assessments of Truman, revealing the complex nature of his character. His daughter, Margaret Truman Daniel, adds her own charm to her dad's special brand of charm in telling stories about the campaign trips.

In addition to contemporary interviews, this special, produced and written by Joel Heller, makes fine use of archival newsreels and old photographs. Perhaps its main weakness is a tendency to play down the weaknesses of Harry S. - his tendency to shoot from the hip in his many personal feuds and, some might think, his unhesitating use of the atomic bomb on Hiroshima. Historian William Leuchtenburg, however, does say on camera that, although most people now acknowledge that the dropping of the bomb in the circumstances was understandable, ''What does continue to trouble people is that Truman showed so little concern about an action that had such devastating consequences.''

Truman set the guidelines for today's presidential actions, Walter Cronkite explains in the program: ''By understanding his presidency we begin to understand the world we live in today. We see why we are in Korea, why we became involved in Vietnam, why we invaded Grenada, why we send military aid to Central America, the beginning of the nuclear arms race, America's special relationship with Israel, our support of NATO, and our preoccupation with the cold war.''

'Political Life of Allard K. Lowenstein'

While humility is a great part of the legacy of Harry Truman, it plays a very small role in the legacy of political activist Allard Lowenstein. Energetic compassion would be more like it.

''Citizen: The Political Life of Allard K. Lowenstein,'' conceived by ''M*A*S*H's'' B. J. Hunnicutt and Mike Farrell, produced and edited by Julie Thompson, is a straightforwardly partisan history of what some would call a ''bleeding heart'' liberal, a sincere defender of civil rights who switched from on-the-march activism to in-the-field political campaigning. The film is a prime example of political and politicized biography.

Utilizing still photography, archival film footage, and current interviews, the film traces Lowenstein's life from his New York City origins, through his University of North Carolina and Yale Law School days, then on to his South African involvement, his voter drive in the American South, his opposition to the United States involvement in Vietnam, his efforts to ''dump'' President Johnson, and finally his own election to Congress and eventual search for a constituency.

Lowenstein's political assassination by a former associate in 1980 is blessedly not part of the graphics, although it is referred to at the end.

Although in general the narrationless film tends to glorify Lowenstein as an apostle of a certan kind of liberal compassion, there are hints that to some he was annoyingly obstinate and divisive factor in his unbending approach to what he called political ''idealism.''

Every now and then the film intersperses short interviews with his children, who say poignantly revealing things about their late father. They knew him best, and it is their judgment that needs to be heard the clearest.

''Allard Lowenstein believed that the doing is of the essence,'' says author David Halberstam, one of the more than 30 people interviewed in the course of this determinedly serious show. Well, the ''doing'' of the ''Citizen'' film itself has caught much of the heady, single-minded essence of Allard K. Lowenstein.