"THE SURVIVAL OF ISRAEL is not a political issue," Jimmy Carter once said. "It's a moral imperative."

Of course, political expediency and moral respectability are not mutually exclusive. For years, the U.S./Israeli "special relationship" served America's strategic interests as well as its ethical ideals.

No longer. Israel is still dependent on American military and financial support, but the U.S. is running out of Realpolitik reasons to continue providing it.

Last week, Alan Dershowitz stood on the Widener steps to exhort supporters of the Jewish state to "make the case for Israel." His case had nothing to do with U.S. strategic interests. It had nothing to do with the Middle East balance of power. It had everything to do with "the rightness of the Israeli cause."

"Unless we convince the world that support for Israel is fundamentally a human rights issue, a moral issue, we will lose," Dershowitz warned.

He's right. And that's scary.

"IN STATESMANSHIP get the formalities right; never mind about the moralities," Twain's Pudd'nhead Wilson declared.

Nowadays, few would agree with ultrarealists like Thucydides, Machiavelli, Hobbes or Pudd'nhead--ethical concerns can and do affect the alliance behavior of some states.

But the strongest bonds between sovereign nations are undoubtedly those held together by a solid community of interests, those that benefit both parties.

Until recently, the benefits America derived from its close relationship with Israel clearly outweighed the alliance's costs. The U.S. had four self-interested reasons to pledge money and might to the Jewish state:

1. Bolster a "strategic asset." Israel was a key component of America's fervent struggle to contain Communism during the Cold War. Rather than station American troops in the Middle East as it did in Western Europe and the Far East, the U.S. relied on Israel's quick-to-mobilize national army to keep the Evil Empire's influence out of the region.

2. Maintain American credibility. Once the U.S. made its initial rhetorical commitments to Israel, it could not afford to rescind them. In the zero-sum bipolar world, the U.S. feared that nonsupport for one of its allies would send others scurrying to the Soviet Union for protection. In the spirit of Machiavelli, America has preferred to reassure the Western bloc that its resident superpower would remain "a true friend."

3. Promote Middle East stability. To a certain extent, "Middle East stability" is an oxymoron. Arabs and Israelis rarely see eye to eye. More often, they see eye-for-an-eye. But the U.S. has had a strong stake in preventing massive conflagrations in this oil-rich, strategically vital region.

On one hand, U.S. support for its encircled ally has aimed to even out the regional balance of power. Although most Arab nations remain committed to Israel's eventual destruction, they have hesitated before attacking an American-built military machine backed by American military guarantees.

On the other hand, the U.S. has tried to restrain Israel from undertaking preemptive strikes against its Arab neighbors or from escalating conflicts that have already begun. Massive aid packages have given the U.S. the leverage to apply the carrot as well as the stick to rein in its often bellicose ally.