"The Life and Assassination of the Kingfish," which airs tonight at 9 on Channel 4, is a true cautionary tale from the relatively short life and rousing times of Huey P. Long.

The lessons are simple. Don't trust your life on the operating table to a political hack. Don't let the boys back home talk you into gerrymandering a judge out of office. And don't let Hollywood recreate your flamboyant, complex career in a mere 92 minutes or so of Prime-time TV.

Long, whose "share the wealth" and "every man a king" rallying cries had carried him from the state railroad commission in 1918 to the U.S. Senate, died from gunshot wounds inflicted by the son-in-law of the threatened judge in September, 1935. He was shot in the rotunda of the state capitol he had built.

Tonight's "docu-drama" races through Long's career by flashbacks as he lies dying in a hospital across from the capitol - much of the program was shot on location - but unless the viewer is familiar with the story, it makes only a scattered kind of sense.

The Kingfish is played by Edward Asner, who does well despite an overheated script that portrays Long as the archetypal Southern loudmouth for the most part and ignores the social forces that catapulated him onto the national scene, where his canny appeals to the Depression poor and his cleverness with the media of the day made even Franklin D. Roosevelt nervous to the point of vindictiveness.

This political stereotyping on TV has led to a couple of other overworked conventions which tonight's script scrupulously observes - the endless shots of well-scrubbed rural types lounging against their wagons, or hunkering down beside fences; and the high-minded Eastern journalist (tonight's spouts Mencken, incidentally) who lectures not only the miscreant pol but the yokels who work for small newspapers as well.

A couple of weeks back, NBC reportedly removed "Kingfish" from tonight's schedule, prompting a change from Thomas Moore, president of Tomorrow Entertainment (which produced it' that it had been yanked because of pressure from Long's son, Sen. Russel P. Long (D-La.).

The show was scheduled after denials from both Long and the network that any such pressure had been applied. Instead, an NBC spokesman said, some last-minute changes due to legal questions and production revisions had prompted a premature announcement.

Last fall, however, Sen. Long did meet with writer-director Robert Collins and others connected with the show to complain about the film's interpretation of several aspects of his father's life.

These reportedly included the inference that Long had instituted the gerrymandering and aspects of the Kingfish's personal life which in tonight's version are reduced to an unexplained visit to his death bed by a pretty brunette.

Modifications of the original version that resulted undoubtedly contribute to the confusion of the story line tonight.

But for the viewer willing to pay close attention there are good performances, not only from Asner, but from Diane Kagan as his wife Rose and particularly Fred Cook as Earl Long, who very nearly steals the show.

On close listening, Long's verbatim stump speeches also remind us that much of what he said 45 years ago still obtains.

And several of the things his oftencorruptde machine pioneered - free textbooks, abolition of the poll tax - foioneered - free textbooks, abolition of the poll tax - foreshadowed the best of our immediate past.