This year it is the question of moving the U.S. Embassy to Jerusalem that has Walter F. Mondale and Sen. Gary Hart (D-Colo.) trading charges about who is a better friend to Israel and Secretary of State George P. Shultz warning Congress about the potentially dire consequences of such a move.

Five months ago, when Sen. Daniel Patrick Moynihan (D-N.Y.) introduced a little-noticed bill to transfer the embassy from Tel Aviv to the capital in Jerusalem, he planted a seed that has blossomed into a major topic of diplomatic anxiety and political campaign rhetoric.

The Jerusalem debate is the latest variation on a quadrennial theme that gets sounded incessantly in every presidential election year. It stems from the competition between aspirants for the White House and Congress to win Jewish votes and campaign contributions by demonstrating the constancy of their support for Israel.

In this year's reprise, the Moynihan bill, together with companion legislation sponsored in the House by Rep. Tom Lantos (D-Calif.), has become the catchall test of this constancy, with almost half the members of Congress supporting the bills.

Despite the anxieties of diplomats who fear that the move will do irreparable harm to U.S. relations with the Moslem world and the chagrin of Jewish leaders who privately concede that it is not the most pressing of Israel's priorities, the embassy issue threatens to turn into a runaway that could drag even reluctant politicians into its wake.

That phenomenon is most evident now in New York where Hart and Mondale, vying for the 252 presidential delegates to be elected in next Tuesday's primary, have been wooing the state's sizable Jewish voting bloc in a running debate about which of them has been most ardent in backing the proposed embassy move.

Mondale has tried to extract mileage from charges that Hart is a late-comer to the idea, having initially said he would favor the embassy transfer if it were negotiated to the satisfaction of Arab states. Hart has responded by accusing Mondale of having endangered Israel's security when, as vice president in the Carter administration, he supported the sale of F15 jet fighters to Saudi Arabia.

In a state where 30 percent to 40 percent of Democratic voters are Jewish, both candidates have ample practical reasons for trying to burnish their pro-Israel credentials to the highest possible sheen. They are keenly aware that political strategists still cite the New York Democratic primary four years ago as "the one that Cy Vance lost for Jimmy Carter."

That is a reference to an incident shortly before the 1980 primary when the Carter administration supported a U.N. Security Council resolution containing critical references to Israel's control of Jerusalem and then, for reasons that never have been explained fully, disavowed its vote. However, in subsequent testimony before Congress, President Carter's secretary of state, Cyrus R. Vance, insisted that the administration still supported parts of the resolution.

Vance's refusal to repudiate all aspects of the resolution made front-page headlines in New York newspapers and was regarded as one of the principal factors in Carter's loss of the 1980 primary there to Sen. Edward M. Kennedy (D-Mass.).

Israeli leaders, however, have tended to regard such election-year politics as a mixed blessing. There is a popular axiom among Israeli officials: "What we fear most is the year after an American presidential election year."

Successful candidates often discover, after taking office, that some of the promises made in the heat of a campaign do not square with wider U.S. interests and then seek escape hatches.

Addressing a national meeting of B'nai B'rith during the 1980 campaign, Ronald Reagan harshly attacked Carter's sale two years earlier of F15s to the Saudis and scornfully called attention to Carter's unwillingness to say whether he would sell the Saudis such additional equipment for the jet fighters as advanced missiles and long-range fuel tanks.

Although he did not say so, the clear implication of Reagan's remarks was that Israel would not have to fear such a development under a Reagan presidency. Yet one of Reagan's first major actions after becoming president was a decision, made despite vehement Israeli objections, to provide Saudi Arabia with the additional F15 equipment and Airborne Warning and Control System (AWACS) radar surveillance planes.

Many supporters of Israel remember what happened in Canada in 1979 when Conservative Party leader Joe Clark won the prime minister's office on a platform that included a promise to move his country's embassy to Jerusalem. Clark's subsequent repudiation of his promise in the face of Arab pressures helped give his government a reputation for ineptitude and was a factor in his being voted out of office after only nine months.

President Reagan and the State Department have given top priority to sidetracking the Moynihan-Lantos bills. They argue that putting the embassy in Jerusalem would compromise the longstanding U.S. position that the future status of the disputed city should be decided through negotiation and would cripple efforts to counter charges in the Arab world that the United States is too biased toward Israel to be an impartial mediator in the Middle East.

The administration also is fearful that shifting the embassy could trigger anti-American violence.

Still, there is a big question about whether these concerns, together with arguments about whether Congress has the constitutional authority to decide where the embassy should be located, will make much headway in an election year.

Even some of Reagan's normally staunch Republican supporters in Congress--among them Rep. Trent Lott of Mississippi, the House minority whip; Rep. Guy Vander Jagt of Michigan, chairman of the National Republican Congressional Committee, and Rep. William S. Broomfield of Michigan, ranking Republican on the Foreign Affairs Committee--are cosponsors of the legislation.

On the other hand, many influential American Jewish organizations, while endorsing the Moynihan bill, have not pushed support beyond obligatory lip service.

That has raised hope in the administration that the legislation can be pigeonholed until after the November election or, failing that, be watered down to make its language non-binding. If not, administration officials say, Reagan will not hesitate to veto the bill.

But that is something that the president, who has his hopes for making big inroads into the Jewish vote, obviously would prefer not to do. Whether it comes to a showdown will depend on how the candidates, in Congress and the presidential race, read the results of the New York primary and other forthcoming contests that could define more clearly how significant the issue of an embassy in Jerusalem is likely to be.