ONE CAN EXPECT a certain amount of mudslinging, hyperbole and unsubstantiated assertion from any Presidential candidate. But even the most cynical observers should be offended by President Reagan's attempt last week to blame the failure of his Lebanon policy on too much public debate.

He claimed that public outcry and Congrssional disagreement over the United States role in Lebanon "hindered the ability of our diplomats to negotiate, encouraged more intransigence from the Syrians, and prolonged the violence." It is not necessary to evaluate thoroughly American policy objectives in the Middle East to see that the Administration's program was handicapped by far more than public outcry. The President's last-ditch attempt to find a scapegoat for his fiasco betrays an awareness of the magnitude of his blunder.

Moreover, he exhibits questionable ethics by choosing to publicly blame the Lebanon policy on Congress and still take credit for the United States economic recovery, in which Congress also played a substantial role.

More dangerous than his jabs at Congressional democrats, however, is the assault on the very structure of American democracy implicit in Reagan's speech. Besides challenging the concept of separation of powers and the system of checks and balances. Reagan would suppress all public opposition to his policies for the sake of maintaining our credibility abroad. The President is right to underscore the potentially positive impact of outward unity in international negotiations, but he goes too far in asking for a blank check both from Congress and from the American public.

"You can't win foreign policy with 535 voices hollering in the background," complained a senior White House official, echoing Reagan's complaint. It seems the President has forgotten that he was one of these voices of dissent only four years ago. And, more importantly, the statement illustrates two problematic elements in the Reagan world view. First, foreign policy should not be "run"; rather, it must be formulated with consideration to various perspectives, national and global, and to long term implications. Furthermore, in a democracy, foreign policy formulation must occur against a backdrop of opinion from a minimum of 535 people and, ideally, with participation from the general population.

LAST WEEK'S STATEMENTS make clear Reagan's preference for Presidential tyranny and convenient voter apathy in the foreign policy arena--preferences undeniably contrary to democratic ideals.