THE RECENT MAYORAL election in Chicago may be seen someday as a watershed in American coalition politics.

It has been widely suggested, of course, that Democrat Harold Washington's narrow margin of victory may reflect the continuing disruption of the Democratic coalition created by Franklin D. Roosevelt. Much less noted, however, was another development: the surprising level of support among Chicago's Jews for the Washington candidacy.

This may suggest that the coalition of blacks and Jews that shaped the civil rights movement for 40 years has weathered the "affirmative action" and "Third World" storms. It is unwise, of course, to read too much into any single election, much less a local one, but there was enough at least to encourage those of us who look for a renewal of this coalition.

This development, virtually ignored on election night, has become even more obscured by the battle between Mayor Washington and the City Council's old guard, led by Alderman Edward R. (Fast Eddie) Vrdolyak. But it could have more long-lasting consequences than the results of that dispute.

On election night, we were told that Harold Washington gained the support of almost all of Chicago's blacks and of 18 percent of the city's white voters. Some commentators also noted that Washington's victory was assured by his strong showing in the city's "liberal, affluent Lake Shore area on the North side."

Those who looked more closely discovered that only about 6 or 7 percent of Washington's white support came from Polish voters. He did somewhat better among Chicago's Irish and Italian ethnic voters, about 11 percent.

The breakthrough occurred in the Jewish community. Mayor Washington's own polls show that he won 50 percent of the Jewish vote, a figure that becomes startling when we recall that Bernard Epton, his Republican opponent, was an active member of Chicago's Jewish community.

This evidence is reinforced by the fact that the "white, liberal, affluent Lake Shore area" that made the critical difference corresponds to the city's greatest concentration of Jewish voters. There seems little doubt that a black-Jewish urban coalition came together to elect Washington.

Why the Jewish vote? If you talk to leaders of Chicago's Jewish community, they will tell you it was because Harold Washington is identified with the traditional program that has kept Jews overwhelmingly Democratic. On civil rights, civil liberties, aid to education and other social issues, commitments of the black and Jewish communities overlap, even as their specific needs for governmental services may diverge.

The racial appeal of the Epton campaign ("Bernie Epton, before it's too late!") also seems to have offended Jewish sensibilities. Rather than make Jews feel "white," it apparently reminded them that they, too, are a minority -- and that the slogan could just as well be used against them.

Mayor Washington's tracking surveys indicated that "before it's too late" jarred the Chicago Jewish community. So did the joke going around the city in the last days of the campaign: that "only a black could get us to vote for a Jew."

But where do the two communities go from here? Can they concentrate on the issues that unite them and mute those that have strained relations in the past?

That clearly depends on the leaders of both groups in Chicago, and the signs so far are encouraging. Mayor Washington has a history of support from Jewish voters and a strong record from his days in Congress on issues of concern to the Jewish community. A number of Chicago's nationally known Jewish leaders also accepted his invitation to serve on his transition team.

If this renewed alliance is built upon, it could be a vital step toward restructuring the nationwide coalition that was so effective in Congress in the 1960s and into the 1970s.

This certainly would be an arduous task, one which would require considerable help from organized labor and which ultimately would have to address the concerns of the most estranged Roosevelt-coalition partner, Catholic blue-collar workers. But it is by no means an impossible chore, and it is one that would have immense consequences if successful.

So it is well worth keeping an eye on what happens in Chicago -- and not just in the City Council fight.