The "Campaign of the Lost," the MASA-Jewish Agency advertising campaign that asked Israelis to identify young Jews in danger of assimilation and connect them to the MASA program, was stupid. The explanation that it was directed at the Israeli public was absurd. MASA wrongly engaged in a kind of noisy marketing that is not appropriate when serious Zionist endeavors are at stake. It was both ineffective and counter-educational. In preferring "spin" to a serious public presentation of its case, MASA emulated an Agency task force that planned a few years ago to encourage aliyah by "selling Israel" through slick marketing, a nonsensical idea luckily aborted before a lot of money was wasted. Similarly, some Israeli authorities plan to improve the country's international image through a "rebranding" campaign. These are futile efforts that come at the expense of dealing seriously with urgent needs - admittedly, a much more difficult undertaking.

But MASA's misguided PR stunt should not cause Zionist leaders and organizations to retreat from an essentially correct, substantive message: The large number of out-marriages (a term I prefer to the bland "intermarriage," and surely to the Nazi term "mixed marriage") means a loss of Jews. The causal chain is clear and statistically deterministic: Marrying a non-Jew, which of course is the right of every Jew as an individual, reduces Jewish influences on one's offspring and increases the probability that they will disengage from the community. Efforts to draw children and grandchildren of out-marriages to the Jewish people should be heightened, but success is likely to be limited, and significant losses are sure to occur.

Contrary to classical Zionist thinking, Israel is not a secure haven for Jews in the physical sense, nor is one needed for most Diaspora Jews. Negating the justification of life in the Diaspora is incorrect, both in the normative sense and in terms of realpolitik. Thriving Jewish communities outside Israel that interact intensely and also compete with Israel, bolster the vitality, creativity and likelihood of survival of the Jewish people. But it is Israel, with its well-entrenched Jewish identity and identification, that is a safe haven against assimilation, even if the nature of what it means to be Jewish changes over time here.

Therefore, aliyah remains an important means of strengthening the Jewish people as a whole, though its modes should change to suit modern conditions. This includes "partial aliyah" - that is, facilitating multiple residences - something proposed by the Jewish People Policy Planning Institute when I served as its founding president.

This brings us to the really serious mistake resulting from the MASA campaign: Diaspora leaders who attacked it did not limit themselves to criticizing the marketing blunder, but struck at the very foundations of Zionism by vociferously denying the seriousness of the loss of Jews caused in the Diaspora by assimilation and out-marriages, and by refusing to recognize the effectiveness of MASA-like programs and, of course, aliyah, in tempering this dangerous reality. Therefore, while the new chairman of the Agency was right to halt the campaign, Zionist leaders should have strongly criticized the denial of the truth by some strident Diaspora leaders and insisted on the validity of MASA's main message. Not doing so constituted a clear loss of Zionist nerve.

This is not the first instance of glaring Zionist loss of nerve. Last June the Agency's board of governors voted to separate the chairmanship of the Agency from that of the World Zionist Organization (WZO). Though I agree with the desire of the Diaspora leadership to oust most of the Israeli apparatchiks who are active in the WZO, they chose the wrong solution. Instead, the "Jewish Agency for Israel" should have been remodeled into the "Jewish People Agency," which would be entrusted with strengthening the life of Jewish people worldwide, with Israel at its core. That new body's mission should include major efforts both to reduce assimilation and attract offspring of out-marriages to the Jewish people, and to encourage aliyah in ways that will not significantly weaken the vitality of Diaspora communities. This requires fusing a revamped Jewish Agency and WZO, rather than separating them.

Zionist leaders worldwide should have insisted on such a quantum leap, which is essential if the Agency is to facilitate the long-term thriving of the Jewish people. But, again, Zionist nerve failed.

Loss of nerve is a major cause of the decline of civilizations, movements and states. Further loss of Zionist nerve must be avoided at the peril of endangering our future. Zionism should be reenergized. Only in that way will it fulfill its mission of strengthening the Jewish people worldwide and of Israel as their core state, including through activities such as MASA and encouraging aliyah.

The writer is a professor emeritus of political science at the Hebrew University of Jerusalem and was founding president of the Jewish People Policy Planning Institute.