Despite circumstantial evidence that Ambassador Robert Neumann was a victim of the pro-Israeli lobby when he was forced to resign as ambassador to Saudi Arabia, his ouster by President Reagan and Secretary of State Alexander Haig had a profound purpose: to avoid offending Menachem Begin on the eve of major Mideast peace moves.

The experienced, respected Neumann, an early Reagan backer who ran the president-elect's State Department transition team, on July 20 privately attacked Haig's performance on ABC's "Issues and Answers" the previous day as one that "made me want to vomit." What unsettled Neumann's stomach was Haig's studied refusal to criticize Israel's bloody air raid on Beirut.

To Al Haig, it was heresy: a subordinate floating a policy line critical of Israel and Menachem Begin that was totally out of phase with the soft Reagan-Haig line. It undercut the Reagan-Haig effort to minimize criticism of Begin so that a beleaguered Begin, believing himself unfairly treated, would not use his power even more irresponsibly, jeopardizing imminent Reagan peace moves.

Quickly informed of Neumann's criticism to at least one member of Congress, Haig summoned him July 23 and read the riot act. The next day, Haig went to the Oval Office and emerged with the president's complete approval to demand Neumann's resignation.

This quick dispatch of an intimate ally of the president's national security assistant, Richard V. Allen, and a trusted Reaganite might have seemed on the harsh side except for another pro-Begin ploy by the Reagan high command during that same week.

Clearly motivated by the Reagan-Haig soft-on-Begin line, White House chief of staff James Baker III publicly chided two of the president's closest friends -- Deputy Secretary of State William Clark and Secretary of Defense Caspar Weinberger -- for their gently critical remarks about Begin after the Beirut raid. Baker's rebuke was mild compared with the terminal treatment of Neumann, but his theme was identical: Reagan will not tolerate criticism of the prime minister of Israel by anyone in his administration at this particularly sensitive moment of Reagan's first diplomatic move into the dangerously unstable Middle East.

Circumstantial evidence that Neumann fell afoul of the pro-Israeli lobby, rather than tripping himself up in the Reagan-Haig policy of avoiding giving offense to Begin, goes back to early January. When the ambassador was named head of Reagan's transition team, he was the target of a three-day front-page attack in Ha'aretz, one of Israel's most respected newspapers.

Ha'aretz focused its attack on an article written by Neumann in the Spring 1979 issue of Washington Quarterly, published by Georgetown University's Center for Strategic and International Studies. Neumann wrote: "A solution of the Palestinian problem . . . means almost certainly, whether we want it or not, and few people really want it, involvement, directly or indirectly, of the PLO [Palestine Liberation Organization]."

That made Newmann a marked man in Israel. The attack by Ha'aretz, however, had not the slightest visible effect on the fledgling Reagan administration.

A more sinister attack on Newmann appeared in the July 17 issue of Middle East Policy Survey, a "confidential" pro-Israeli newsletter with a reputation for accuracy. Quoting from a secret cable Neumann recently sent to the State Department describing a conversaton he had had with Crown Prince Fahd about the AWACS planes Reagan wants to sell Saudi Arabia, the Survey quoted an annonymous State Department official: "He [Neumann] would make up anything to help get the AWACS through" Congress.

Haig's closed-door demand for Neumann's resignation during a 3 p.m. meeting July 25 swept like wildfire through the pro-Israeli lobby. By Monday night, a leading Israeli newspaper, Yediot Ahronot, had the full story from its Washington correspondent, Wolf Blitzer, long before any announcement.

But joy over Neumann's demise among the friends of Israel is a mere offshoot to the real purpose of the president and his secretary of state. With the cease-fire in Lebanon hanging on a thread, they will use whatever political muscle is necessary to avoid giving Begin any pretext for breaking that thread and perhaps plunging the Middle East into full-scale war.

Despite condemnation of Israel's Baghdad raid and the continuing holdup of F16 fighter planes for Israel, Reagan is committed to placate Begin between now and his September state visit to Washington, following Egyptian President Anwar Sadat's visit this week. In the hopeful Reagan-Haig view, the time to talk turkey to Begin will be in September, when Reagan's diplomatic skills will get their toughest challenge to date: West Bank autonomy, an end to Jewish settlements, Mideast peace and an anti-Soviet "strategic consensus."