If any one issue is obstructing the formation of a center ground in American politics, it is abortion. On its face,abortion is as uncompromisable an issue as the American political system has ever confronted. For advocates of choice, abortion is a fundamental right. For the pro-life movement, abortion is murder. Between those two positions there is little room for agreement--and, in fact, the dialogue between the pro-choice and pro-life movements is almost nonexistent.

Yet the mass electorate sees the issue quite differently from the partisans on either side. There is no single majority on abortion in the country; there are two overlapping majorities.

On the one hand, Americans are deeply uneasy with government interference in intimate decisions. Thus, when pollsters pose the abortion issue as a question of whether the choices of individual women or government policy will be binding, the results are a clear pro-choice majority.

Yet when pollsters put the question differently, they get another majority: Most of the country thinks too many abortions are performed, rejects most reasons women give for having them and favors certain restrictions on abortion--such as requiring teen-agers to get parental permission.

Some polls have produced the rather staggering finding that a majority can support legal abortion, even as a majority of the same group considers abortion the equivalent of murder.

This mass ambivalence makes itself felt at the polls in a peculiar way. Many voters simply refuse to base their vote on the abortion issue. Thus in Iowa, in 1990, Sen. Tom Harkin, running on a pro-choice platform, was reelected, and so was Gov. Terry E. Branstad, an ardent right-to-lifer. In 1990, voters handed pro-choice candidates the governorships of Florida and Texas--and pro-life candidates the governorships of Michigan and Ohio.

The 1990 elections, once touted as the nation's abortion referendum, turned out to be something far less. An ambivalent country cast an ambivalent vote.

If ever there were an issue where ambivalence is understandable, it is abortion. The challenge to U.S. politics is to find ways of promoting public policy that speaks to that ambivalence. The problem for the right-to-life movements is that the country as a whole does not accept its absolutist opposition to abortion and is wary of too much government meddling. The problem for the pro-choice movement is that the country shares the right-to-lifers' moral uneasiness with abortion and would like to encourage a moral standard that would reduce the number of abortions.