Of course I'll decide on a candidate - tomorrow

The wild bounces in the polls have puzzled many observers during this presidential campaign. Some of the exaggerated shifts in the standing of George Bush and Michael Dukakis result from a range of often subtle differences in polling methodology. But the most important source of the variations is the inherent softness of what is being assessed. Many millions of voters simply haven't made up their minds.

Once a voter has thought about his electoral choice and made a commitment, we can measure his decision quite satisfactorily. Should he be polled on his choice, using any reasonably framed set of questions, he will tell us whom he favors - giving the same answer each time he is asked. While he may change his mind as the campaign goes on, he isn't likely to. Considered decisions to support a candidate are quite stable.

Large numbers of people, however, do not make a voting decision until very late in the campaign, and some never make it at all. The latter, nonvoters, often pay so little attention to the race that they never form a preference for one candidate or the other. ``Screening'' questions are used in pre-election polling to separate out likely nonvoters - but these efforts meet with only partial success.

Thus pre-election samples, until very late in the campaign, contain in large numbers (a) people who will eventually vote but haven't yet made a decision, and (b) people who never will vote. When asked in a public opinion survey whether they favor Bush or Dukakis, some in both of these groups will offer a spur-of-the-moment choice. We make a terrible conceptual error when we treat these largely unconsidered declarations as though they are decisions.

Historically, a large segment of the electorate made its decision on how to vote very early - because their decisions were based on established party loyalties. That proportion has shrunk dramatically in recent decades, though, and for many cut loose from stable party ties there has been no substitute electoral ``anchor.''

The result is a higher level of indecision and a postponing of the time when the decision is made - sometimes until election day itself. Modern presidential campaigns routinely have larger numbers of undecided voters than those of times past. This poses no special problem for American democracy - but it makes candidates and pollsters very nervous.

We don't know precisely how many people are undecided at various stages in a presidential campaign. Pollsters employ various methods to try to tease out information on the extent of electoral indecision.

Surveys taken by the Gallup Organization immediately after each of the last five presidential elections have asked voters when they decided whom to support. This series gives us a good sense of how the relative level of voter indecisions rises and falls in different types of contests.

Many more voters reached their decisions on whom to support later in 1976 and '80 than in '72 and '84 (see accompanying table). An incumbent was seeking reelection in all four elections. In the first two, however, the incumbent's weaknesses or unpopularity compounded voter indecision.

In 1980, one-quarter of the entire electorate said they made their choice either in the very last days of the campaign or on election day. A large bloc of voters considered Jimmy Carter an inadequate president but at the same time were unsure about Ronald Reagan. Fears that Mr. Reagan might prove ``trigger happy'' or otherwise ``extreme'' was the major factor holding many of these voters back.

In this context of ambivalence and indecision, the televised Carter-Reagan debate just six days before the election had an extraordinary impact. Reagan reassured many who had been undecided that it was safe to take a chance on him after all. A close contest became a landslide.

If 1980 stands at one pole in modern elections, 1984 is at the other. Again, an incumbent was seeking reelection - but this time his standing prompted little indecision. A majority liked the job Reagan had done and wanted him to continue; a minority opposed him, often strongly. Most voters made their decision early.

At this stage in the current campaign, we don't have enough data to locate it in the modern series. It is evident that many voters are still undecided or have made only light commitments that could be blown away by the zephyrs of tomorrow's news.

A recent survey by CBS News and the New York Times found, for example, about three-fifths of likely voters saying they had firmly decided for either Bush or Dukakis (see accompanying chart). The other two-fifths either had not reached a judgment at all, or thought their current preference was soft enough that they might well change it.

Asking respondents whether their opinions of the candidates were favorable, unfavorable, or not formed, produced much the same picture: 30 to 40 percent of probable voters said they had not yet arrived at a judgment on either Bush or Dukakis.

The level of indecision that we have seen thus far in Campaign '88 fits into the range established by recent elections. It is undoubtedly greater than in 1984, but probably a bit less substantial than in 1976 or '80.

Everett C. Ladd is executive director of the Roper Center for Public Opinion Research at the University of Connecticut.