For this first installment of Firing Line broadcast on public television, we have as our guests two men actively seeking to dump President Nixon. Mr. Lowenstein's organization had voted in favor of impeaching him for high crimes and misdemeanors-no, not Watergate, which was still more than a year away, but rather his conduct of the war in Vietnam. For the same reason, Mr. McCloskey had announced that he would challenge the President for the 1972 Republican nomination.