An old-fashioned political scandal involving charges of favoritism and countercharges of demangoguery has turned a courtly, a quiet Senate race in Arkansas into an angry brawl in the final days.

The dispute, which centers on a charge that Gov. David Pryor's supporters sought to influence a natural gas rate-setting decision, casts considerable doubt on recent predictions that Pryor is likely to defeat Rep. Jim Guy Tucker in next Tuesday's runoff election for the Democratic Seante nomination.

Pryor, 43, two-term governor and former congressman, ran first in a four-candidate election two weeks ago. Tucker, 34, who entered the Senate race midway through his first term in the House, edged Rep. Ray Thornton for second place to earn a spot in next week's runoff.

Since the Arkansas Republican Party is extremely weak, the winner of the Democratic runoff will be certain of election to the Senate. And it was clear to both camps that the runoff would go to the candidate who could capture most of Thornton's supporters.

That seems to lie at the root of the current scandal.

Many of Thornton's backers in the intial primary are responsive to the wishes of Thornton's uncles, Jackson T. (Jack) and Wilton R. (Witt) Stephens, who are the richest men in Arkansas and powerful political forces as well.

Last week Pryor's campaign manager, Jack Williams, privately approached the chairman of the state's Public Utility Commission to discuss a pending rate increase request filed by Arkansas-Oklahoma Gas Co., one of Witt Stephens' properties.

Williams and the chairman agree that Williams proposed that a commission staff report critical of the company be kept private until after the runoff election. The commission chairman says Williams also asked that the rate increase be granted, but Pryor's camp denies that.

Tucker's campaign staff heard about the discussion and complained to the utility commission chairman. He responded by calling a press conference to reveal the "ex-parte communication" from Pryor's top campaign aide.

It was a perfect target for Tucker, who has made consumer advocacy a central feature of his campaign. For the past week, Tucker told voters at every campaign stop that Pryor's camp was willing to impose a gas rate hike on consumers to win the political support of the Stephens family.

Pryor has been forced to admit that his campaign manager made a "mistake of the head," although the governor says he personally knew nothing about Williams' contact with the utility commission.

The incident has turned a gentle issueless campaign into an angry series of confrontations and press conferences.At back-to-back press appearances Wednesday, Tucker accused Pryor of "corruption" in office and Pryor respond that Tucker was campaigning on a "total untruth."

A mystery is the pryor campaign manager's need to do any favors for the Stephenses. Political professionals believed that Pryor was likely to win most of the Thornton voters anyway because, the Thornton, he has a rural background.

A poll last week showed Pryor leading Tucker 43 to 36. But this week, everyone agrees, the race can only be called a toss-up.