One of Israel's most respected elder statesmen, the knowledgeable and eloquent Abba Eban, may have reached the end of his political career this week as the result of a new method of choosing candidates for parliament. If so, Israel has inflicted a serious loss on itself.

Eban, now 73, has been foreign minister, deputy prime minister, ambassador to the United Nations, and ambassador to the United States. His sophisticated rhetoric and fluency in six languages entranced audiences abroad, and caused David Ben-Gurion, the founding father of Israel, to call him "The voice of the Hebrew nation."In 1967, when the world was stunned by Israel's lightning victory in the Six Day War, and United Nations sessions preempted daily television shows, Eban's brilliant performance in debate kept the U.N. from demanding that Israel give up its gains in that war.

The astute Eban is losing his post in the Knesset, the 120-seat Israeli parliament as the result of a new system adopted by his Labor Party. Previously, party leaders picked the candidates, but the new system allowed - for the first time - the rank-and-file party members to do the choosing. As a result, more than half the candidates are newcomers and Eban was one of the casualties.

Eban, who lacks a solid political base inside Israel, was more of an intellectual than a party worker, and was perhaps more popular abroad than at home. Eban once said that if outsiders could vote in Israeli elections, he would have been prime minister. His sharp wit also did not sit well at times with his own pragmatic, blunt-spoken countrymen.

The apparent end of Eban's political career is the result of a democratic vote and cannot be faulted on that account. But there is no mistaking the fact that the Knesset will be poorer without him, his knowledge, his skill, and his well-turned phrases.