Picking up after the president when he's been flinging foreign policy pronouncements around the way he did in Kansas City is hard labor, the more so because it's not easy to know where to start. But if your concern is with damage limitation in a delicate, dangerous policy problem of some immediacy, you start where the State Department, in a rare departure from prudent practice, started: with the president's feckless suggestion that the only alternative to the government of President Ferdinand Marcos in the Philippines is a communist takeover.

"I don't think the president was narrowing the situation that far," said State Department spokesman John Hughes. "I think there is certainly recognition on everybody's part that there are other forces working for democratic change in the Philippines."

Only an institution dedicated to diplomacy could have conveyed so decorously the message that the president didn't know what he was talking about. The president displayed an all-too-familiar either/or cast of mind that is entirely consistent with Vice President George Bush's famous tribute to the Marcos regime: "We love your adherence to democratic principles and to democratic process." Reagan, to his credit, did not go that far. He even acknowledged "there are things there in the Philippines that do not look good to us from the standpoint right now of democratic rights." But the alternative, he said, "is a large communist movement to take over the Philippines." That unqualified statement was what shook up State Department policy-makers.

What does not look good is the damning judgment of four of the five members of a commission appointed by Marcos himself to investigate the assassination a year ago of Benigno Aquino Jr. He was the popular and promising leader of the opposition so conspicuously excluded from the president's analysis of the alternatives in the Philippines. The majority found a military conspiracy reaching all the way up the chain of command to Gen. Fabian Ver, chief of staff of the armed forces. Ver is intimately connected to Marcos and his almost equally powerful wife, Imelda. It strains credulity that he could have acted without some sense of their consent.

We are talking, then, about a real crisis and quite probably a real crossroads in the Philippines. Reacting with admirable forcefulness, the State Department has zeroed in not only on the report of the commission's chairman, which portrayed a much narrower, lower-level military "plot," but also on the unanimous findings of the other four commission members. The outcome is going to depend on how seriously Marcos takes the U.S. insistence that "those responsible . . . no matter who they may be, will be held acuntable for this terrible crime." And the answer to that question is going to depend, in turn, on whether he believes that, in the end, the United States eases up rather than risk the alternative, as the President put it in Kansas City, of "throwing (the Philippines) to the wolves and then facing the communist power in the Pacific."

There is no denying the existence of a significant communist guerrilla force in the Philippines. It is probably gaining strength -- in large part owing to the democratic opposition's frustrations in its struggle against the repression of the Marcos regime. That is precisely why the State Department is insistent that this democratic opposition be recognized, respected and afforded a decent opportunity to come to power in the inevitable transition from 19 years of Marcos' rule, half of them under martial law. That's the crucial point that seems to escape the president when he talks about the Philippines.