Every evening a ghost of politics past flickers across thousands of Louisiana television screens: Huey P. Long, arm-waving, hell-raising, leading the faithful in one more round of his political anthem, "Every Man a King."

"They call him Kingfish," the announcer intones as the music fades. "Huey P. Long will be remembered. But this year, in 1980, what he is remembered for most fondly is that he produced a Louisiana son who was to rise to greater heights than he ever achieved . . . Russell Long whose mission is not to overthrow but to work and labor within the system . . . And now Russell Long, son of Huey, is called 'Mr. Chairman,' 'Honorable Senator' and 'Mr. Louisiana.'"

Suddenly the camera shifts to Son of Huey, driving to work in Washington, discoursing on the irrelevancy of dynasty to the congressional meritocracy, and then to Mr. Chairman, promising that the Senate Finance Committee would offer the nation a whopping tax cut.

But lest anyone think that Mr. Louisiana has forgotten his roots, there's a Midwestern Republican, Sen. Bob Dole of Kansas, and a Northeastern Democrat, Sen. Daniel Patrick Moynihan, saying it isn't so. Russell Long is big on state's rights and "somehow state's rights often turns out to be the rights of Louisiana -- have you noticed that?" Moynihan asks Dole. "I've noticed that," Dole responds obligingly.

And so it goes for 30 minutes on prime-time television, the media centerpiece for Long's seventh senatorial campaign, which will probably all be over when the votes are counted in Saturday's primary election.

In Louisiana, anyone who can get at least 50 percent of the vote in the state's wide-open, y'all-come primary can avoid the nuisance and risk of having to run in the general election.

And there is hardly anyone except his main opponent, a young Democratic state legislator named Louis (Woody) Jenkins, a staunch conservative who's trying to paint an unobliging Long into a liberal corner, who doesn't say that Long will get his 50 percent and then some.

In this year of bleak portents for Democratic incumbents, many of Long's colleagues would consider themselves lucky to get just one vote more than 50 percent. But for about 18 months Long has been buzzing around Louisiana like a mosquito, campaigning every bit as strenuously and seriously as his endangered brethren.

Long, a somewhat portly and rumpled figure, at 61, is a bundle of boundless energy, relaxed but restless, even impish as he remembers yet another Huey Long or "Uncle Earl" Long story from his seemingly endless repertoire. He smiles the smile of a choir boy. He is a born politician and appears to love every minute of it.

He flits from a breakfast with black ministers (where he recalls how his father got the poor children of Louisiana their free textbooks) to a Kaiser Aluminum and Chemical Co. luncheon (where he exhorts company officials to expand their already big Louisiana investment).

Among the black clergymen last Thursday, he proclaimed that he's an "all-out Huey Long man," glossing gracefully over the fact that he's also one of corporate America's -- and the oil industry's -- best friends in Washington.

He recalled proudly that Huey Long wanted to "tax the rich to help the poor" and that Uncle Earl, Huey's brother and another star in the Long political galaxy, approached the oil industry on the theory, "Tax 'em good -- they can't hate you more than 100 percent." As for civil rights, he dwelt on what his father did for blacks, not his own record of oposition to major 1960s civil rights legislation.

If there were some familial contradictions there, no one seemed to mind. Huey's son was, as usual, a big hit -- even bigger after he said he'd push a tax amendment to let those of modest means, those who use the short tax form, take deductions for their church contributions.

At the Kaiser luncheon, Long came on strong in a different way. Praised as much by the executives as he was by the preachers, he honed in on one of his favorite causes: expansion of labor-intensive industries like consumer product manufacturing as job-producing spinoffs of existing petrochemical and other refining facilities.

"You've got 5,000 jobs here," he told the Kaiser executives, "bless you, but why not 10,000? Why not make it [aluminum] into finished products . . . make it into a spoon, just anything." The Kaiser men smiled, noncomittally.

Everywhere he goes, Long reminds the home folks of the billions of Dollars that he's helped bring back to Louisiana, from an auto plant for Shreveport to a World's Fair for New Orleans, to say nothing of the $3 billion a year from oil and gas price decontrol that he hardly ever fails to mention.

As for the 1984 World's Fair, his latest trophy, he made it sound like it was all in a day's work for the chairman of the Senate Finance Committee. i

Why, all it took, he told a rally in New Orleans, was a gentle reminder to the Carter administration that its revenue legislation would "move like frozen molasses" through the Finance Committee until New Orleans gets its fair. There may have been other reasons, but New Orleans got the nod for its fair and some federal grants to help it along.

Strange as it may seem to Louisianans, few of whom can remember politics without a Long embellishing the scene, there are good reasons for such seemingly bizarre behavior from one of the nation's wiliest politcians.

Even though his preemptive strike to fend off any opposition scared the GOP just a year after the Republicans captured the governorship for the first time in a century, Long fell short of his dream of a free ride back to the Senate.

Moreover, Jenkins -- the only one of his four challengers who is regarded as a serious contender -- took Louisiana by surprise in getting 41 percent of the vote against Sen. J. Bennett Johnston (D-La.) in 1978. This was double what Jenkins had been expected to get, apparently due in part to the fact that Johnson waited too long to take him seriously.

As in many other states, there is also a strong anti-incumbent, anti-Washington tide coupled with some indication of a more conservative drift -- posing problems for pragmatic, entrenched lawmakers like Long.

Jenkins, for instance, is banking heavily on residual anger toward Long for his vote in favor of the Panama Canal treaties, hoping it will trigger a feeling that Long is too much of a freewheeling power broker to pay heed to his constituents' feelings.

Jenkins also argues that if Long is as powerful in Washington as people say, he's got to accept blame for inflation, recession and other problems. He portrays Long as liberal, arrogant, out of touch. Long represents power, he says, and people aren't impressed with power.

But Jenkins has his problems, too, not the least of which is money. The latest spending tallies indicate that Long, who has taken in $1.2 million in campaign contributions so far, is out-spending Jenkins by about 14 to 1."He [Long] has soaked up the state like a sponge," said a Louisiana reporter. Jenkins says he won't be able to spend more than $100,000 before the election.

The risk for Long, if there is any, is that anything less than Johnston's 59 percent -- perhaps anything less than his own usual 65-to-70 percent -- would be an embarrassment and a sign of weakness for the future.

Long was 29 when he was first elected to the Senate in 1948 to fill out two years of an unexpired term and has since been elected to five consecutive terms, making him fourth ranking in Senate seniority. Rebounding from a drinking problem, an unhappy marriage and an internal threat to his Senate powers, Long is now happily remarried and ensconced securely at the top of the congressional pecking order. So, even at 61, he may well be looking to the future -- to another term, friends say. In any case, he's known for liking to keep his options open.

All of this may be too complicated, other Long watchers suggest. "He worked so hard to scare off his opposition," said one, "but I think he'd miss a Woody Jenkins if he weren't there . . . he loves a good campaign, he's too good at it not to."

Said Long: "You go where your talents take you."