DID THEY catch Jeane Kirkpatrick on "Meet the Press" Sunday in Morazan? Mr. Reagan's ambassador to the United Nations said something to the guerrillas up there in the mountains of El Salvador. She was asked the recurring question of the American policy debate: would the United States, whose influence is critical, support "dialogue" between government and guerrillas before the presidential elections the government now plans to hold by the end of the year? She said, we thought, yes. The question was put to her twice more, and both times her response was the same.

So what is going on? Has not the Reagan administration been insisting vehemently, to the anguish of its critics, that talks are out of the question until the guerrillas lay down their arms and accept the Salvadoran government's electoral scheme? Has the president changed his mind?

We are not sure we understood exactly what the message was. If words have their common meaning, however, Mrs. Kirkpatrick took a long and potentially important step beyond the administration's familiar position that political power in El Salvador must be earned at the polls and not divvied up arbitrarily at a table and so, until elections have been held, there is nothing to talk about. She made at least an opening to the left to help shape "the conditions for full participation of all elements in Salvadoran society willing to participate in those democratic elections." She invited the left to help establish conditions of amnesty and security and to take part in "any kind of discussions necessary to establish open elections."

In recent days the president, sounding again his earlier theme of escalating peril, has called for more military aid to El Salvador and a new role for American advisers. Such appeals are consistent with an intent to pursue a military solution. But such appeals are also consistent with an intent to bolster one's bargaining position. Which is it?

The left does not have to guess. Least of all should it and its friends dismiss these latest signs as a rerun of a position deemed unacceptable in the past. It should test the American-Salvadoran offer. If the opening is too narrow, then the offer of it becomes a natural occasion to try to widen it.