When presidential candidates disagree about the Middle East, it usually is about which of them is the better friend of Israel. Such is certainly the case this year, as Republican George Bush and Democrat Michael Dukakis compete for the support of active and influential Jewish voters.

Neither candidate has advocated radical departures from traditional U.S. policy toward the Middle East, and both have stressed backing of Israel as the paramount American goal in the region. The few differences emerging in the campaign have centered on specific Reagan administration policies. For example, while Bush insists that the administration has been the most pro-Israel one in years, Dukakis asserts that President Reagan has jeopardized Israel's security by selling advanced weapons to Arab countries.The arms sale issue is a perennial one in American politics. When campaigning, most candidates complain about the billions of dollars worth of weapons and military services that the United States sells to Saudi Arabia, Jordan and other Arab countries that technically remain at war with Israel. Once in office, however, presidents tend to view arms sales as useful tools to exert U.S. leverage.

In one of his few direct attacks on Reagan policy, Dukakis has promised to take a harder line on arms sales to Arabs, telling a B'nai B'rith conference: "We will not sell weapons that would threaten the security of Israel to any nation. And we will work to persuade our NATO allies to join us in that policy."

Bush generally skirts the arms issue, but speaking to the same B'nai B'rith group, Bush said the United States can have an alliance with Israel and "still pursue better relations with other countries in the area."

(It is not known whether Bush ever opposed or questioned specific Arab arms sales proposed by the Reagan administration. But Bush has said that he raised concerns about the 1985-86 secret arms sales to Iran, a non-Arab country; however, several Iran-Contra investigations produced no evidence that he actively opposed Reagan's decision to sell weapons to the Tehran regime.)

On most issues regarding the Middle East, however, there is little disagreement between the candidates. Dukakis has endorsed - and Bush has sought to take a measure of credit for - a number of Reagan administration actions geared toward strengthening the military and economic ties between the United States and Israel, including the establishment of joint military planning teams, U.S. financial backing for new Israeli weapons systems and creation of a free-trade zone between the two countries.

Neither candidate has spelled out a clear proposal for reviving the long-stalled peace process between Israel and its Arab neighbors, although both endorse standard formulations of U.S. policy: Washington cannot impose a peace settlement on Israel or force it to negotiate with the Palestine Liberation Organization.

Both men have endorsed some elements of a negotiating plan advanced this year by Secretary of State George P. Shultz. But they have avoided embracing the one element that is most controversial in Israel: an "international conference" to serve as a starting point for direct talks among Israel, Palestinians and Jordan.

In short, not only is neither Bush nor Dukakis willing to stick his neck out very far, but stated differences between them are so few and far between that voters deeply interested in the Middle East may have to use other issues to help them choose which lever to pull on Nov. 8.