While Sen. Joseph R. Biden Jr. (D-Del.) was chairing the hearings on the Supreme Court nomination of Robert H. Bork yesterday, his aides were trying to contain political damage to Biden's presidential prospects from a second round of charges that he had plagiarized others' speeches.

The New York Times reported Saturday that Biden, during remarks at an Aug. 23 Democratic debate in Iowa, quoted at length from a speech of British Labor Party leader Neil Kinnock without crediting him. Aides explained that this was an oversight and that Biden had given the speeches before in which Kinnock was credited.

Yesterday, Knight-Ridder newspapers reported that Biden did much the same thing last February in a speech delivered at the California Democratic Party convention -- only that time he lifted the words of Robert F. Kennedy. During that speech, Biden used language from two Kennedy speeches, without attribution, although one of the Kennedy quotes was attributed in the text distributed to reporters.

Much to the chagrin of the Biden campaign, the incident made the front page of the Des Moines Register.

"Sen. Biden and his team of speechwriters have been one of the most prolific and original in the Democratic Party," responded spokesman Larry Rasky. "We don't need to try to slip one by people to try and make our point." Rasky added that he considers "this to be a game of trivial pursuit being played by one of our opponents." He declined to name the opponent.