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Pro-Israel political power in Washington is at a zenith today, with powerful supporters at both ends of Pennsylvania Avenue and clear across the political spectrum.

But underneath, the foundation may be facing serious erosion.

Eating away at the grassroots base is a growing alienation among Conservative and Reform Jews from an Israel that seems increasingly in the grips of ultra-religious leaders.

If that trend, or even the perception, continues, it could spell trouble for pro-Israel political activism. More than 90 percent of American Jews are non-Orthodox, and they are the glue that holds the pro-Israel movement together.

Pro-Israel groups like the American Israel Public Affairs Committee (AIPAC) have largely stayed away from religious questions. In fact, there was once a debate within AIPAC about whether it was a "Jewish organization" or a "pro-Israel organization." The latter view prevailed.

Most Christian groups that support Israel emphasize their religious motivation, while Jewish organizations largely focus on economic, security-related, political and diplomatic issues.

With few exceptions, such as the Union of Orthodox Jewish Congregations of America, it is unusual to see Orthodox groups lobbying on Capitol Hill in support of U.S.-Israel relations. Instead, their political activity is aimed largely at enhancing U.S. government support for their own institutional programs and interests: a medal memorializing the Lubavitcher rebbe, grants for yeshivas in Israel and elsewhere, assistance for various group projects.

Recent developments in Jerusalem could have a serious impact on the core of American pro-Israel political activism.

Israel's "Bar-On Affair" revolves around charges that Aryeh Deri, head of the Sephardi Shas Party and a member of Knesset, offered to swap Shas' 10 votes on the controversial Hebron agreement in January in exchange for Prime Minister Benjamin Netanyahu appointing an attorney general who would draft a favorable plea bargain with Deri, who is on trial for corruption.

But the would-be attorney general, Likud loyalist Roni Bar-On, was considered such a legal lightweight that he was forced to quit within 48 hours.

Separately, Shas and the other religious parties have pressured Netanyahu to introduce legislation to codify the Orthodox establishment's control over religious conversions in Israel.

Netanyahu, when he was in Washington earlier this month, brushed off the effort as nothing more than preserving the status quo. In truth it is intended to overturn a Supreme Court decision that opened the door to recognizing the Reform and Conservative movements. A compromise is now being debated.

But Reform and Conservative movements do not have much optimism because their strength in Israel is negligible, in contrast to the ultra-religious parties, which hold 23 seats and the balance of power in Netanyahu's government.

The Labor Party announced that its Knesset members would vote against the conversion bill, and Labor leader Shimon Peres denounced it as a "grave mistake" that "would divide the Jewish people."

But all four candidates to succeed Peres as Labor's leader ducked out of voting on the matter, lest they offend the religious parties with whom they dream of one day playing "Let's Make a Deal."

Both parties have had opportunities, particularly as partners in the unity governments of the 1980s, to end the excessive and destructive power of the religious parties, but they consistently let it pass because each prayed that someday soon it would have a chance to outflank the other by making an alliance with the religious and thus regain the most influence.

Yuval Rabin, the son of the late prime minister, was in Washington recently drumming up support for his new pro-peace group, Dor Shalom, when he ran into a barrage of questions and criticism over the conversion law. Until then, he said, he had not realized how much the influence of the ultra-religious "alienates American Jewry." Such laws, he said, "don't make sense in the best of times, and especially at a time when we need the support" of American Jewry and the U.S. government.

Many of the religious parties use their political clout to impose their religious rules on others and to wrest ever-increasing public funding for their yeshivas and their students, many of whom never serve in the military or become taxpayers. This creates broad resentment among non-Orthodox Israelis, but even most of them do not understand the impact on diaspora Jewry of such things as the conversion law.

Non-Orthodox American Jews see such laws and other restrictions as attempts to delegitimize them.

When one right-wing group, the Union of Orthodox Rabbis of the United States and Canada, declares that Conservative and Reform movements are "not Judaism," and a spokesman for the Orthodox Agudath Israel of America says religious pluralism is just another word for "anarchy," the alienation of mainstream American Jewry will grow.

Already the first signs are evident. In some communities there is intense debate about how much and even whether local federation contributions to the United Jewish Appeal should even reach Israel. Rabbi Ismar Schorsch, chancellor of the Conservative Jewish Theological Seminary, has urged members of his movement and Jewish organizations to end financial support for groups opposed to recognition of non-Orthodox causes in Israel.

The perception, accurate or not, of a direct link between Israel's religious establishment and the country's corruption scandals, lack of pluralism and regression in the peace process could corrode American Jewish support for the Jewish state.