Vice President Bush is the only 1988 presidential candidate to decline to appear on an interview program sponsored by Harvard's Kennedy School of Government, to be broadcast by PBS. Marvin Kalb, director of the school's Center for Press and Politics and moderator for the show, said yesterday that after months of negotiations with Bush's campaign -- "unlike negotiations with any other campaign" -- he received a definite no on Tuesday. The official explanation from Bush spokesman Peter Teeley was that the vice president is "overbooked," Kalb said.

But Kalb said he heard other explanations from other senior Bush aides. One told him that "an hour of substantive talk with Marvin Kalb will not advance Bush's candidacy." Perhaps the aide feared that would be especially true if part of the time were devoted to questions about Bush's involvement in the Iran-contra affair, as Kalb intended.

Another aide told Kalb that Bush suffers from a "preppy image," and as a Yale man he would not be helping his image by accepting a Harvard invitation.

Kalb said he was "terribly disappointed." Bush "is asking the American people to give him the hardest job in the world, and all we are asking is that he spend an hour answering some serious questions," Kalb said.

"The irony is that when Bush pulled out, we moved Gary Hart in" to appear Jan. 3, Kalb said.