THERE IS a useful symmetry to the process set formally in motion yesterday by Israeli Prime Minister Menachem Begin to schedule elections in July. It lets Israelis select the government they think best suited to the new circumstances created by the changes in Washington, by their experience under Camp David so far and by the deterioration is Israel's economy and morale.

At this point the polls suggest that Labor will win big -- perhaps so big that for the first time an Israeli government can ignore the narrowly focused National Religious Party. It could even be that Shimon Peres could form a government without reliance on the party faction led by his rival. Yitzhak Rabin. This would give him unusual real power.

No one who knows Mr. Begin, however, will count him out. The peace treaty with Egypt is his monument. He may turn to his own advantage the internatioanl support already evident for Mr. Peres. His resoluteness plays into the national mood of siege.

Many Israelis, despairing of reaching any satisfactory settlement with Palestinians, will listen to Mr. Peres' promise of more purposeful economic management. Others will be drawn by Labor's pledge to attempt within the Camp David context to negotiate a peace treaty with Jordan based on territorial compromise on the West Bank, meanwhile addressing those "Palestinian personalities and bodies who will recognize Israel and reject terror tactics."

Positioning himself for the next phase, King Hussein has stepped up his denunciations of the "Jordanian option" as a Palestinian non-starter and sellout. Egypt's President Sadat dismisses it as a detour from the Camp David road, and one that leads nowhere. Amony Palestinians, however, there is, amid the cynicism about the concept, a lingering curiosity about the terms. This is where Labor's policy will finally succeed or fail.

What Mr. Reagan must do voer the next few months is clear: Take his own measured reading of the Camp David autonomy talks. Do nothing to give the United States any larger part than it will have anyway in the Israeli campaign. Use the six-month electoral interval to think out a comprehensive regional policy. And, with the sense of trust and intimacy the United States has always enjoyed with Israel, prepare to deal with whoever wins.