On top of old Nebo, all covered with voters, a siew of office-seekers turned out the other day to chew over politics and poultry at one of Arkansas' grand old political traditions: the annual Mount Nebo Chicken Fry.

Candidates running for everything from senator to city clerk in Arkansas' primary elections Tuesday came to this Ozark peak to woo votes among the 10,000 people who gathered for a day of eating and oratory in celebration of the chicken, the state's chief agricultural export.

Farmers sat down on bales of hay and used their straw hats to swat the horseflies. Children romped barefoot in the soft dust beneath the pines. Teen-aged boys turned their pickups in a makeshift parking lot beside a soybean field. And all day long political speeches poured forth from the flag draped flat-bed truck that served as a platform for the candidates.

It was, all in all, a classic tableau of old-time politics, southern style. But there was one thing about this year's chicken fry that did not match the old political mold: the politicians.

The people running for election in Arkansas this year seem to be a far cry from the race - baiting country boys who formed the stereotype of the southern politican until recently.

The typical new breed candidate, here as elsewhere in the South, is an urbane, neatly tailored figure of vigorous youth who is liberal on racial questions and fuzzy enough on other issues to convince rural voters he is a conservative without losing his liberal image in the cities.

The shift to a new politics here is most apparent this spring in the Democratic primary race for the Senate seat that was held for 35 years by John L. McClellan, a rough-hewn, rightwing country lawyer who died last winter at the age of 81.

There are three major Democratic contenders for the seat - the state's governor and two congressmen - and none fits, the McClellan mold.

The leader is clearly David Pryor, and amiable 43-year-old moderate who almost toppled McClellan in the 1972 Senate race and has since served two terms as governor.

Pryor served three terms in Congress in the late 1960s, and made a name for himself as an early advocate of the concerns of older people. When House leaders rejected his proposal for a special committee on the aging, Pryor set up a committee of his own with private funds in a trailer down the street from the Capitol.

With similar ingenuity, Pryor has become by far Arkansas' best known politician. His upbeat, easygoing campaign style, together with Arkansas' growing prosperity during his four years as governor, gave him a commanding head start when the Senate race began.

But hard work and heavy spending by Pryor's two chief rivals have cut his margin. The governor is still likely to lead the ticket Tuesday, but he will probably not take 50 percent of the vote. Thus a runoff election on June 13 seems certain.

The two men chasing Pryor, Jim Guy Tucker and Ray Thornton, are both Ivy League-trained lawyers who began itching for a Senate seat after brief tours of duty in the House.

Tucker, 34, is the paradigm of the bright young man in a hurry.

He began setting records of the "youngset ever" category when he made Eagle Scout at the age of 12, and has kept up the momentumever since: he was prosecutor of the state's biggest county at 27 and state attorney general at 29 before he went to Congress in 1976. Barely halfway through his first ouse tern, he announced his candidacy for the Senate.

On the comapign trail, Tucker is literally running for office. He lopes through shopping centers, rattles off speeches and rushes off to the next spot like a traveler whose plane is due to leave in 30 seconds.

Thornton, 49, three-term congressman, is precisely the opposite.

He ambles down the streets, greeting voters in a style so unassuming as to be almost apologetic. When he finds someone who wants to chat, Thornton hooks his thumbs in his pockets and stands around talking while his campaign aides try to push him along to the next scheduled appearance.

Despite the down-home image, Thornton is a scion of Arkansas' richest family. His uncles, Jack and Witt Staphens, control banks and gas companies throught the South as well as one of the nation's largest brokerage houses.

The family connection has been a blessing and a curse for the Thornton campaign. The candidate has had trouble convincing voters that he is not running to extend the family empire. But he had little difficulty raising money; his contributions, largely from business interest, exceed $600.000, and he has borrowed another $200,000, from banks in which his uncles have interests.

Tuckers has raised about $425,000 for campaign, and Pryor $360,000. All three candidates have poured the money into media advertisements that stress personality and rarely issues.

"Every campaign I've ever been in," Pryor said the other day, "there's been some issue that if you went to a shopping center, 20 people would hit you with it. But now there's just a calm."

Thornton has tried to win points by noting that he voted against the Social Security tax increase in the House last year, while Tucker supported it. Tucker has taken Pryor to task for failing to improve the public schools. But neither these nor other issues have won much attention.

Instead, the Senate race here seems to be a matter of style. On that basis, the favorite for election would have to be Pryor, whose personable manner has helped him win easily in the last two statewide elections.