MR. REAGAN'S ASSERTION that fraud and violence "perpetrated largely by the ruling party" call into question the credibility of the Philippine elections will help to clear the air -- air that had been made unclear by his own earlier statements. He may have checked the damaging perception that, notwithstanding the cheating, President Marcos was still qualified for leadership in American eyes. But the crisis in the Philippines is still deepening. Yesterday, President Marcos had the national assembly, which he controls, proclaim him the official winner. It was a shameless act.

But Mrs. Aquino does not accept it. She refuses to accept a Marcos steal. She does not have the official levers available to a sitting president, but she has a hold on the loyalties of the vast number of Filipinos who voted for her. Her strategy amounts to the continuation of elections by the means of civil protest -- mobilizing the people first by "prayer rallies" and later perhaps by strikes, starting in one or a few places and expanding the locales, attempting by degrees to bring the government and the economy to a halt.

There is considerable risk in this strategy. Street demonstrations could produce violence or invite the provocative attentions of the hard left and thus provide the government with a pretext for violence or for proclaiming anew martial law -- a development that would have its own provocative and sinister effects. No one who knows Ferdinand Marcos will underestimate the tenacity with which he holds on to power.

Mrs. Aquino has a commitment to nonviolence and speaks for a broad democratic movement that has reacted with remarkable calmness and order so far to the government's election dirty tricks. But in an atmosphere of spreading public protests, she could hardly guarantee that Philippine communists would not try to make big trouble. This unpresumptuous novice has startled many observers with her political skills; her leadership may now be tested as never before.

A great many people in the Philippines feel they were robbed in the elections -- robbed with the evident consent, initially anyway, of the country they had been led to believe was the patron of their democratic heritage. The result is to put an even heavier burden on the mission of presidential emmissary Philip Habib to do what the United States can to bring about a political result in the Philippines that is consistent with the people's will.