DOVER, DEL., SEPT. 9 -- Rep. Thomas R. Carper (D) won renomination Saturday in a landslide. With 96 percent of the returns counted, Carper had 91 percent to 9 percent for his challenger, Daniel Rappa.

Carper faces Republican businessman Ralph O. Williams, a political newcomer, in November.

Seeking a record fifth term in Delaware's only seat in the House, Carper led a reform movement last year that ousted New Castle County Democratic Party Chairman Eugene T. Reed Sr., who has since been indicted on political corruption charges.

Reed backed Rappa, a millionaire developer.

"We were looking for some kind of reaffirmation that the reforms we undertook a year ago were right, and indeed I think what we have . . . is a ringing endorsement that the Democratic Party in Delaware is on the right track," Carper said in a victory speech.

"I've never won more than 68 percent of the voters on anything. Winning over 80 percent is hard to believe," said Carper, whose political experience includes six years as state treasurer.

Democrats said the victory sets the stage for a Carper gubernatorial bid in 1992.

Rappa engaged in name-calling throughout the challenge and tried to link Carper to the national savings and loan debacle.