Arkansas Gov. Bill Clinton held the lead in his race for the Democratic nomination for a sixth term yesterday, while a former utility chief was in a tight battle against a sheriff turned congressman in the raucous GOP gubernatorial primary.

Clinton had 54 percent to 40 percent for his main challenger, Tom McRae, ex-president of the Winthrop Rockefeller Foundation, with 87 percent of the vote reported.

With all votes counted in Kentucky, former Louisville mayor Harvey Sloane defeated state schools Superintendent John Brock, 59 percent to 41 percent, for the Democratic nomination to meet Sen. Mitch McConnell (R) in the fall. In the GOP primary, McConnell easily defeated perennial candidate Tommy Klein, 89 percent to 11 percent.

Brock promptly pledged unity for the fall campaign: "Tonight we're going to tango and be together," he said.

In the 1st Congressional District of Arkansas, Rep. Bill Alexander (D), a 22-year veteran, defeated Osceola attorney Mike Gibson, a political newcomer, 54 percent to 46 percent with 86 percent of the vote reported.

In the Louisville area, 10-term incumbent Rep. Romano L. Mazzoli (D), who campaigned without money from political action committees, won nomination for an 11th term, but got less than 50 percent of the vote in a three-way race. He had 45 percent against former television reporter Jeffrey Hutter's 32 percent and Alderman Paul Bather's 22 percent with all precincts reported.

In Arkansas, Rep. Tommy Robinson, former police chief and sheriff from Pulaski County, had 49 percent of the GOP gubernatorial primary vote to 51 percent for Sheffield Nelson, former head of Arkla Inc., the major natural gas utility in Arkansas, with 71 percent of the vote counted.

Sen. David Pryor (D-Ark.) had no primary opposition and faces a write-in foe in November.

Clinton, 43, was the nation's youngest governor when first elected in 1978. He lost a reelection bid in 1980, but was elected in 1982, 1984 and 1986, when the two-year term for governor was doubled.

Clinton became the object of jokes in 1988 because of his meandering speech introducing Massachusetts Gov. Michael S. Dukakis at the 1988 Democratic National Convention.