The lifting of the dense fog known as Israeli poltics reveals that in the election of June 30, Menachem Begin won a stupendous victory. He significantly increased the parliamentary strength of his backers without help from any other prominent Israeli leaders, and at the expense of foreigners he liked least.

Begin promises to be more difficult than ever. So the United States needs to develop a blend of toughness and understanding that can foster Begin's sense of statesmanship as against his itch for petty, tactical gains.

By the Israeli measure, what Begin achieved in the election is striking enough. He increased the strength of the Likud coalition that he lends from 43 to 48 seats in the Knesset. Together with 13 votes of the religious parties, he commands an absolute one-vote majority of the 120 seats. He can add to that five seats held by splinter parties. So he holds 66 seats against a minority of 54. Since the religious bloc is fragmented, Begin actually enters the new parliament in a much stronger position.

The more so as many Israeli figures of note abandoned the prime minister in his hour of need. Ezer Weizman, who had helped him in 1977, subsequently resigned as Begin's defense minister. Moshe Dayan quit as Begin's foreign minister, Yigal Hurvitz as his minister of finance and Shmuel Tamir as his justice minister. So Begin's victory was a one-man victory.

During the run-up to the election, furthermore, two of Begin's foreign foes were beaten at the polls -- Jimmy Carter in the United States and Valery Giscard d'Estaing in France. Their defeats made Begin's win in Israel all the sweeter.

Immediately after the election, he showed the world what it is like to be insufferable in victory. He lectured the leader of the opposition, Shimon Peres, as if he were a schoolboy. He threatened to take out missiles moved by Syria into Lebanon. He opened a line of communication with the leader of the Moral Majority, Jerry Falwell -- the better to undo an American embargo on shipment of sophisticated fighter planes to Israel and to combat an administration promise to sell AWACS surveillance planes to Saudi Arabia.

The stakes in the Middle East are so high, and the margin of safety so narrow, that continued performance by the Israeli prime minister in that vein could be genuinely dangerous. As matters now stand, Begin threatens American ties with moderate states, especially Saudi Arabia. He could drive Egyptian President Sadat away from the peace accord with Israel and force Syria further into Soviet arms. Even war cannot be excluded.

The best hope against these dangers is Begin himself. Though assertive to the point of irrationality on tactical issues, he can take the larger view. He did it after Sadat's visit to Jerusalem in agreeing to evacuate the Sinai desert. It is not inconceivable that, with his majority secure and with Carter and Giscard out of the way, Begin will calm down and see that his great opportunity is to come to terms with the moderate Arabs, including the moderate Palestinians.

But the United States can play a part in edging Begin toward responsibility. Maintaining Israel's qualitative military superiority is one requirement. In that respect, lifting the hold placed on shipment of fighter planes is essential.

In ending the embargo, however, American officials ought to take Begin up on his repeated insistence that everything is different now because the United States and Israel are allies. The fact is that Israel has not recently behaved as a good ally should behave. It has acted as though that alliance meant an American blank check for everything Begin considered to be in his country's national interest. It has created situations at times -- notably the raid on the Iraqi nuclear installation -- that were harmful to American interests.

Another opportunity presents itself when Begin visits the United States this fall. The agenda for the talks should be fixed with meticulous care. There has to be agreement on the ending of Israeli settlements on the occupied West Bank of the Jordan River. There has to be a clear understanding that there will be some Israeli give on negotiations with Egypt to accord more self-rule to the Palestine Arabs living on the West Bank and in the Gaza Strip.

For the fact s that Begin has put Israel on a collision course with disaster. As a good ally, the United States has an obligation to save him, and his country, from his worst self.