A group of top campaign officials for Sen. Joseph R. Biden Jr. (D-Del.), who withdrew from presidential race Sept. 23, announced yesterday that they will support Sen. Paul Simon (D-Ill.). They include Lowell Junkins, Biden's Iowa chairman and 1986 Democratic gubernatorial candidate; David Wilhelm, his Iowa coordinator; Mike Lux, his deputy national political director; Larry Grisolano, his Iowa field director, and Bruce Koeppl, his Iowa political director.

"It is time for our party to begin to unify behind a candidate who can be nominated and elected," Junkins said at a news conference at Simon's Iowa headquarters. "The only way we can hope for that unity is to have a candidate who bridges the gaps from one side of our party to the other -- from the Hart supporters to the Mondale supporters. Paul Simon provides us an excellent opportunity to do that."

Junkins estimated that 85 to 90 percent of Biden's Iowa staff is joining the Simon camp. Phil Roeder, the state Democratic Party's communications director, called the addition "an organizational shot in the arm."

Simon, who appeared at three news conferences across Iowa with Junkins and the other former Biden staffers, said the new support will help build on his growing momentum in Iowa. "This is beyond any question the biggest day of my campaign since the day of my announcement," he said.